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20.7.2012 Official
Journal
of
the
European
Union L
193/1
II
(Non-legislative acts)
REGULATIONS
COMMISSION REGULATION (EU) No 640/2012
of 6 July 2012
amending, for the purpose of its adaptation to technical progress, Regulation (EC) No 440/2008
laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament
and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals
(REACH)
(Text with EEA relevance)
THE EUROPEAN COMMISSION,
used for experimental purposes, in accordance with
Directive 2010/63/EU of the European Parliament and
of the Council of 22 September 2010 on the protection
of animals used for scientific purposes ( 3 ) and Council
Directive 86/609/EEC of 24 November 1986 on the
Having regard to the Treaty on the Functioning of the European
approximation of laws, regulations and administrative
Union,
provisions of the Member States regarding the protection
of animals used for experimental and other scientific
purposes ( 4 ). Stakeholders have been consulted on this
draft.
Having regard to Regulation (EC) No
1907/2006 of
18 December 2006 of the European Parliament and of the
Council concerning the Registration, Evaluation, Authorisation
and Restriction of Chemicals (REACH), establishing a European
(3) Regulation
(EC)
No
440/2008
should
therefore
be
Chemicals Agency, amending Directive 1999/45/EC and
amended accordingly.
repealing Council Regulation (EEC) No 793/93 and Commission
Regulation (EC) No 1488/94 as well as Council Directive
76/769/EEC and Commission Directives 91/155/EEC,
93/67/EEC, 93/105/EC and 2000/21/EC ( 1 ), and in particular
(4) The
measures
provided
for
in
this
Regulation
are
in
Article 13(3) thereof,
accordance with the opinion of the Committee estab
lished under Article 133 of Regulation (EC)
No 1907/2006,
Whereas:
HAS ADOPTED THIS REGULATION:
(1) Commission
Regulation
(EC)
No
440/2008
( 2 ) contains
the test methods for the purposes of the determination
Article 1
of the physico-chemical properties, toxicity and eco-
toxicity of substances to be applied for the purposes of
The Annex to Regulation (EC) No 440/2008 is amended in
Regulation (EC) No 1907/2006.
accordance with the Annex to this Regulation.
Article 2
(2) It
is
necessary
to
update
Regulation
(EC)
No
440/2008
to
include with priority new and updated alternative test
This Regulation shall enter into force on the third day following
methods recently adopted by the OECD, in order to
that of its publication in the Official Journal of the European
obtain a reduction of the number of animals to be
Union.
( 1 ) OJ L 396, 30.12.2006, p. 1.
( 3 ) OJ L 276, 20.10.2010, p. 33.
( 2 ) OJ L 142, 31.5.2008, p. 1.
( 4 ) OJ L 358, 18.12.1986, p. 1.

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This Regulation shall be binding in its entirety and directly applicable in all Member States.
Done at Brussels, 6 July 2012.
For the Commission
The President
José MANUEL BARROSO

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ANNEX
The Annex to Regulation (EC) No 440/2008 is amended as follows:
1. Chapter B.42 is replaced by the following:
‘B.42. SKIN SENSITISATION: LOCAL LYMPH NODE ASSAY
INTRODUCTION
1. OECD
Guidelines
for
the
Testing
of
Chemicals
and
EU
Test
Methods
based
on
them
are
periodically
reviewed
in
light of scientific progress, changing regulatory needs, and animal welfare considerations. The original Test Method
(TM) for the determination of skin sensitisation in the mouse, the Local Lymph Node Assay (LLNA; OECD Test
Guideline 429; Chapter B.42 of this Annex) was adopted previously (1). The details of the validation of the LLNA
and a review of the associated work have been published (2) (3) (4) (5) (6) (7) (8) (9) (10) (11). The updated LLNA
is based on the evaluation of experience and scientific data (12). This is the second TM to be designed for
assessing skin sensitisation potential of chemicals (substances and mixtures) in animals. The other TM (i.e. OECD
Test Guideline 406; Chapter B.6 of this Annex) utilises guinea pig tests, notably the guinea pig maximisation test
and the Buehler test (13). The LLNA provides advantages over B.6 and OECD Test Guideline 406 (13) with regard
to animal welfare. This updated LLNA TM includes a set of Performance Standards (PS) (Appendix 1) that can be
used to evaluate the validation status of new and/or modified test methods that are functionally and mechanis
tically similar to the LLNA, in accordance with the principles of OECD Guidance Document No 34 (14).
2. The LLNA studies the induction phase of skin sensitisation and provides quantitative data suitable for dose-
response assessment. It should be noted that the mild/moderate sensitisers which are recommended as suitable
positive control chemicals (PC) for guinea pig test methods (i.e. B.6; OECD Test Guideline 406) (13) are also
appropriate for use with the LLNA (6) (8) (15). A reduced LLNA (rLLNA) approach, which could use up to 40 %
fewer animals is also described as an option in this TM (16) (17) (18). The rLLNA may be used when there is a
regulatory need to confirm a negative prediction of skin sensitising potential, provided there is adherence to all
other LLNA protocol specifications, as described in this TM. Prediction of a negative outcome should be made
based on all available information as described in paragraph 4. Before applying the rLLNA approach, clear
justifications and scientific rationale for its use should be provided. If, against expectations, a positive or
equivocal result is obtained in the rLLNA, additional testing may be needed in order to interpret or clarify the
finding. The rLLNA should not be used for the hazard identification of skin sensitising test substances when dose-
response information is needed such as sub-categorisation for Regulation (EC) No 1272/2008 on classification,
labelling and packaging of substances and mixtures and UN Globally Harmonised System of Classification and
Labelling of Chemicals.
DEFINITIONS
3. Definitions
used
are
provided
in
Appendix
2.
INITIAL CONSIDERATIONS AND LIMITATIONS
4. The LLNA provides an alternative method for identifying potential skin sensitising chemicals. This does not
necessarily imply that in all instances the LLNA should be used in place of guinea pig tests (i.e. B.6; OECD
Test Guideline 406) (13), but rather that the assay is of equal merit and may be employed as an alternative in
which positive and negative results generally no longer require further confirmation. The testing laboratory should
consider all available information on the test substance prior to conducting the study. Such information will
include the identity and chemical structure of the test substance; its physicochemical properties; the results of any
other in vitro or in vivo toxicity tests on the test substance; and toxicological data on structurally related chemicals.
This information should be considered in order to determine whether the LLNA is appropriate for the substance
(given the incompatibility of limited types of chemicals with the LLNA — see paragraph 5) and to aid in dose
selection.
5. The
LLNA
is
an in vivo method and, as a consequence, will not eliminate the use of animals in the assessment of
allergic contact sensitising activity. It has, however, the potential to reduce the number of animals required for this
purpose. Moreover, the LLNA offers a substantial refinement (less pain and distress) of the way in which animals
are used for allergic contact sensitisation testing. The LLNA is based upon consideration of immunological events
stimulated by chemicals during the induction phase of sensitisation. Unlike guinea pig tests (i.e. B.6; OECD Test
Guideline 406) (13) the LLNA does not require that challenge-induced dermal hypersensitivity reactions be
elicited. Furthermore, the LLNA does not require the use of an adjuvant, as is the case for the guinea pig
maximisation test (13). Thus, the LLNA reduces animal pain and distress. Despite the advantages of the LLNA
over B.6 and OECD Test Guideline 406, it should be recognised that there are certain limitations that may
necessitate the use of B.6 or OECD Test Guideline 406 (13) (e.g. false negative findings in the LLNA with certain
metals, false positive findings with certain skin irritants (such as some surfactant type chemicals) (19) (20), or

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solubility of the test substance). In addition, chemical classes or substances containing functional groups shown to
act as potential confounders (21) may necessitate the use of guinea pig tests (i.e. B.6; OECD Test Guideline 406)
(13). Further, based on the limited validation database, which consisted primarily of pesticide formulations, the
LLNA is more likely than the guinea pig test to yield a positive result for these types of test substances (22).
However, when testing formulations, one could consider including similar substances with known results as
benchmark substances to demonstrate that the LLNA is functioning properly (see paragraph 16). Other than
such identified limitations, the LLNA should be applicable for testing any substances unless there are properties
associated with these substances that may interfere with the accuracy of the LLNA.
PRINCIPLE OF THE TEST
6. The
basic
principle
underlying
the
LLNA
is
that
sensitisers
induce
proliferation
of
lymphocytes
in
the
lymph
nodes
draining the site of test substance application. This proliferation is proportional to the dose and to the potency of
the applied allergen and provides a simple means of obtaining a quantitative measurement of sensitisation.
Proliferation is measured by comparing the mean proliferation in each test group to the mean proliferation in
the vehicle treated control (VC) group. The ratio of the mean proliferation in each treated group to that in the
concurrent VC group, termed the Stimulation Index (SI), is determined, and should be ≥ 3 before classification of
the test substance as a potential skin sensitiser is warranted. The procedures described here are based on the use of
in vivo radioactive labelling to measure an increased number of proliferating cells in the draining auricular lymph
nodes. However, other endpoints for assessment of the number of proliferating cells may be employed provided
the PS requirements are fully met (Appendix 1).
DESCRIPTION OF THE ASSAY
Selection of animal species
7. The mouse is the species of choice for this test. Young adult female mice of CBA/Ca or CBA/J strain, which are
nulliparous and non-pregnant, are used. At the start of the study, animals should be between 8-12 weeks old, and
the weight variation of the animals should be minimal and not exceed 20 % of the mean weight. Alternatively,
other strains and males may be used when sufficient data are generated to demonstrate that significant strain
and/or gender-specific differences in the LLNA response do not exist.
Housing and feeding conditions
8. Mice should be group-housed (23), unless adequate scientific rationale for housing mice individually is provided.
The temperature of the experimental animal room should be 22 ± 3 °C. Although the relative humidity should be
at least 30 % and preferably not exceed 70 %, other than during room cleaning, the aim should be 50-60 %.
Lighting should be artificial, the sequence being 12 hours light, 12 hours dark. For feeding, conventional
laboratory diets may be used with an unlimited supply of drinking water.
Preparation of animals
9. The animals are randomly selected, marked to permit individual identification (but not by any form of ear
marking), and kept in their cages for at least five days prior to the start of dosing to allow for acclimatisation
to the laboratory conditions. Prior to the start of treatment all animals are examined to ensure that they have no
observable skin lesions.
Preparation of dosing solutions
10. Solid chemicals should be dissolved or suspended in solvents/vehicles and diluted, if appropriate, prior to
application to an ear of the mice. Liquid chemicals may be applied neat or diluted prior to dosing. Insoluble
chemicals, such as those generally seen in medical devices, should be subjected to an exaggerated extraction in an
appropriate solvent to reveal all extractable constituents for testing prior to application to an ear of the mice. Test
substances should be prepared daily unless stability data demonstrate the acceptability of storage.
Reliability check
11. Positive control chemicals (PC) are used to demonstrate appropriate performance of the assay by responding with
adequate and reproducible sensitivity as a sensitising test substance for which the magnitude of the response is
well characterised. Inclusion of a concurrent PC is recommended because it demonstrates competency of the
laboratory to successfully conduct each assay and allows for an assessment of intra- and inter-laboratory repro
ducibility and comparability. A PC for each study is also required by some regulatory authorities and therefore
users are encouraged to consult the relevant authorities prior to conducting the LLNA. Accordingly, the routine
use of a concurrent PC is encouraged to avoid the need for additional animal testing to meet such requirements
that might arise from the use of a periodic PC (see paragraph 12). The PC should produce a positive LLNA

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response at an exposure level expected to give an increase in the SI > 3 over the negative control (NC) group. The
PC dose should be chosen such that it does not cause excessive skin irritation or systemic toxicity and the
induction is reproducible but not excessive (i.e. a SI > 20 would be excessive). Preferred PC are 25 % hexyl
cinnamic aldehyde (Chemical Abstracts Service (CAS) No 101-86-0) in acetone: olive oil (4:1, v/v) and 5 %
mercaptobenzothiazole (CAS No 149-30-4) in N,N-dimethylformamide (see Appendix 1, Table 1). There may
be circumstances in which, given adequate justification, other PC, meeting the above criteria, may be used.
12. While inclusion of a concurrent PC group is recommended, there may be situations in which periodic testing (i.e.
at intervals ≤ 6 months) of the PC may be adequate for laboratories that conduct the LLNA regularly (i.e. conduct
the LLNA at a frequency of no less than once per month) and have an established historical PC database that
demonstrates the laboratory’s ability to obtain reproducible and accurate results with PCs. Adequate proficiency
with the LLNA can be successfully demonstrated by generating consistent positive results with the PC in at least
10 independent tests conducted within a reasonable period of time (i.e. less than one year).
13. A concurrent PC group should always be included when there is a procedural change to the LLNA (e.g. change in
trained personnel, change in test method materials and/or reagents, change in test method equipment, change in
source of test animals), and such changes should be documented in laboratory reports. Consideration should be
given to the impact of these changes on the adequacy of the previously established historical database in
determining the necessity for establishing a new historical database to document consistency in the PC results.
14. Investigators should be aware that the decision to conduct a PC study on a periodic basis instead of concurrently
has ramifications on the adequacy and acceptability of negative study results generated without a concurrent PC
during the interval between each periodic PC study. For example, if a false negative result is obtained in the
periodic PC study, negative test substance results obtained in the interval between the last acceptable periodic PC
study and the unacceptable periodic PC study may be questioned. Implications of these outcomes should be
carefully considered when determining whether to include concurrent PCs or to only conduct periodic PCs.
Consideration should also be given to using fewer animals in the concurrent PC group when this is scientifically
justified and if the laboratory demonstrates, based on laboratory-specific historical data, that fewer mice can be
used (12).
15. Although the PC should be tested in the vehicle that is known to elicit a consistent response (e.g. acetone: olive
oil; 4:1, v/v), there may be certain regulatory situations in which testing in a non-standard vehicle (clinically/
chemically relevant formulation) will also be necessary (24). If the concurrent PC is tested in a different vehicle
than the test substance, then a separate VC for the concurrent PC should be included.
16. In instances where test substances of a specific chemical class or range of responses are being evaluated,
benchmark substances may also be useful to demonstrate that the test method is functioning properly for
detecting the skin sensitisation potential of these types of test substances. Appropriate benchmark substances
should have the following properties:
— structural and functional similarity to the class of the test substance being tested;
— known physical/chemical characteristics;
— supporting data from the LLNA;
— supporting data from other animal models and/or from humans.
TEST PROCEDURE
Number of animals and dose levels
17. A minimum of four animals is used per dose group, with a minimum of three concentrations of the test
substance, plus a concurrent NC group treated only with the vehicle for the test substance, and a PC (concurrent
or recent, based on laboratory policy in considering paragraphs 11-15). Testing multiple doses of the PC should
be considered, especially when testing the PC on an intermittent basis. Except for absence of treatment with the
test substance, animals in the control groups should be handled and treated in a manner identical to that of
animals in the treatment groups.

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18. Dose and vehicle selection should be based on the recommendations given in references (3) and (5). Consecutive
doses are normally selected from an appropriate concentration series such as 100 %, 50 %, 25 %, 10 %, 5 %,
2,5 %, 1 %, 0,5 %, etc. Adequate scientific rationale should accompany the selection of the concentration series
used. All existing toxicological information (e.g. acute toxicity and dermal irritation) and structural and physico
chemical information on the test substance of interest (and/or structurally related substances) should be considered
where available, in selecting the three consecutive concentrations so that the highest concentration maximises
exposure while avoiding systemic toxicity and/or excessive local skin irritation (3) (25). In the absence of such
information, an initial pre-screen test may be necessary (see paragraphs 21-24).
19. The vehicle should not interfere with or bias the test result and should be selected on the basis of maximising the
solubility in order to obtain the highest concentration achievable while producing a solution/suspension suitable
for application of the test substance. Recommended vehicles are acetone: olive oil (4:1, v/v), N,N-dimethylform
amide, methyl ethyl ketone, propylene glycol, and dimethyl sulphoxide (19) but others may be used if sufficient
scientific rationale is provided. In certain situations it may be necessary to use a clinically relevant solvent or the
commercial formulation in which the test substance is marketed as an additional control. Particular care should be
taken to ensure that hydrophilic test substances are incorporated into a vehicle system, which wets the skin and
does not immediately run off, by incorporation of appropriate solubilisers (e.g. 1 % Pluronic L92). Thus, wholly
aqueous vehicles are to be avoided.
20. The processing of lymph nodes from individual mice allows for the assessment of inter-animal variability and a
statistical comparison of the difference between test substance and VC group measurements (see paragraph 35). In
addition, evaluating the possibility of reducing the number of mice in the PC group is feasible when individual
animal data are collected (12). Further, some regulatory authorities require the collection of individual animal data.
Nonetheless, pooled animal data may be considered acceptable by some regulatory authorities and in such
situations, users may have the option of collecting either individual or pooled animal data.
Pre-screen test
21. In the absence of information to determine the highest dose to be tested (see paragraph 18), a pre-screen test
should be performed in order to define the appropriate dose level to test in the LLNA. The purpose of the pre-
screen test is to provide guidance for selecting the maximum dose level to use in the main LLNA study, where
information on the concentration that induces systemic toxicity (see paragraph 24) and/or excessive local skin
irritation (see paragraph 23) is not available. The maximum dose level tested should be 100 % of the test
substance for liquids or the maximum possible concentration for solids or suspensions.
22. The pre-screen test is conducted under conditions identical to the main LLNA study, except there is no assessment
of lymph node proliferation and fewer animals per dose group can be used. One or two animals per dose group
are suggested. All mice will be observed daily for any clinical signs of systemic toxicity or local irritation at the
application site. Body weights are recorded pre-test and prior to termination (Day 6). Both ears of each mouse are
observed for erythema and scored using Table 1 (25). Ear thickness measurements are taken using a thickness
gauge (e.g. digital micrometer or Peacock Dial thickness gauge) on Day 1 (pre-dose), Day 3 (approximately 48
hours after the first dose), and Day 6. Additionally, on Day 6, ear thickness could be determined by ear punch
weight determinations, which should be performed after the animals are humanely killed. Excessive local skin
irritation is indicated by an erythema score ≥ 3 and/or an increase in ear thickness of ≥ 25 % on any day of
measurement (26) (27). The highest dose selected for the main LLNA study will be the next lower dose in the pre-
screen concentration series (see paragraph 18) that does not induce systemic toxicity and/or excessive local skin
irritation.
Table 1
Erythema Scores
Observation Score
No erythema
0
Very slight erythema (barely perceptible)
1
Well-defined erythema
2
Moderate to severe erythema
3
Severe erythema (beet redness) to eschar formation preventing grading of erythema
4

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23. In addition to a 25 % increase in ear thickness (26) (27), a statistically significant increase in ear thickness in the
treated mice compared to control mice has also been used to identify irritants in the LLNA (28) (29) (30) (31)
(32) (33) (34). However, while statistically significant increases can occur when ear thickness is less than 25 %
they have not been associated specifically with excessive irritation (30) (32) (33) (34).
24. The following clinical observations may indicate systemic toxicity (35) (36) when used as part of an integrated
assessment and therefore may indicate the maximum dose level to use in the main LLNA: changes in nervous
system function (e.g. pilo-erection, ataxia, tremors, and convulsions); changes in behaviour (e.g. aggressiveness,
change in grooming activity, marked change in activity level); changes in respiratory patterns (i.e. changes in
frequency and intensity of breathing such as dyspnea, gasping, and rales), and changes in food and water
consumption. In addition, signs of lethargy and/or unresponsiveness and any clinical signs of more than slight
or momentary pain and distress, or a > 5 % reduction in body weight from Day 1 to Day 6, and mortality should
be considered in the evaluation. Moribund animals or animals obviously in pain or showing signs of severe and
enduring distress should be humanely killed (37).
Main study experimental schedule
25. The experimental schedule of the assay is as follows:
— Day 1: Individually identify and record the weight of each animal and any clinical observation. Apply 25 μL of
the appropriate dilution of the test substance, the vehicle alone, or the PC (concurrent or recent, based on
laboratory policy in considering paragraphs 11-15), to the dorsum of each ear.
— Days 2 and 3: Repeat the application procedure carried out on Day 1.
— Days 4 and 5: No treatment.
— Day 6: Record the weight of each animal. Inject 250 μL of sterile phosphate-buffered saline (PBS) containing
20 μCi (7,4 × 10 5 Bq) of tritiated ( 3 H)-methyl thymidine into all test and control mice via the tail vein.
Alternatively, inject 250 μL sterile PBS containing 2 μCi (7,4 × 10 4 Bq) of 125 I-iododeoxyuridine and 10 –5 M
fluorodeoxyuridine into all mice via the tail vein. Five hours (5 h) later, humanely kill the animals. Excise the
draining auricular lymph nodes from each mouse ear and process together in PBS for each animal (individual
animal approach); alternatively excise and pool the lymph nodes from each ear in PBS for each treatment
group (pooled treatment group approach). Details and diagrams of the lymph node identification and
dissection can be found in reference (12). To further monitor the local skin response in the main study,
additional parameters such as scoring of ear erythema or ear thickness measurements (obtained either by using
a thickness gauge, or ear punch weight determinations at necropsy) may be included in the study protocol.
Preparation of cell suspensions
26. A single-cell suspension of lymph node cells (LNC) excised bilaterally using the individual animal approach or
alternatively, the pooled treatment group approach is prepared by gentle mechanical disaggregation through 200
micron-mesh stainless steel gauze or another acceptable technique for generating a single-cell suspension. The
LNC are washed twice with an excess of PBS and the DNA is precipitated with 5 % trichloroacetic acid (TCA) at
4 °C for 18h (3). Pellets are either resuspended in 1 mL TCA and transferred to scintillation vials containing
10 mL of scintillation fluid for 3 H-counting, or transferred directly to gamma counting tubes for 125 I-counting.
Determination of cellular proliferation (incorporated radioactivity)
27. Incorporation of 3 H-methyl thymidine is measured by β-scintillation counting as disintegrations per minute
(DPM). Incorporation of 125 I-iododeoxyuridine is measured by 125 I-counting and also is expressed as DPM.
Depending on the approach used, the incorporation is expressed as DPM/mouse (individual animal approach)
or DPM/treatment group (pooled treatment group approach).
Reduced LLNA
28. In certain situations, when there is a regulatory need to confirm a negative prediction of skin sensitising potential,
an optional rLLNA protocol (16) (17) (18) using fewer animals may be used, provided there is adherence to all
other LLNA protocol specifications in this TM. Before applying the rLLNA approach, clear justifications and
scientific rationale for its use should be provided. If a positive or equivocal result is obtained, additional
testing may be needed in order to interpret or clarify the finding.

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29. The reduction in number of dose groups is the only difference between the LLNA and the rLLNA test method
protocols and for this reason the rLLNA does not provide dose-response information. Therefore, the rLLNA
should not be used when dose-response information is needed. Like the multi-dose LLNA, the test substance
concentration evaluated in the rLLNA should be the maximum concentration that does not induce overt systemic
toxicity and/or excessive local skin irritation in the mouse (see paragraph 18).
OBSERVATIONS
Clinical observations
30. Each mouse should be carefully observed at least once daily for any clinical signs, either of local irritation at the
application site or of systemic toxicity. All observations are systematically recorded with records being maintained
for each mouse. Monitoring plans should include criteria to promptly identify those mice exhibiting systemic
toxicity, excessive local skin irritation, or corrosion of skin for euthanasia (37).
Body weights
31. As stated in paragraph 25, individual animal body weights should be measured at the start of the test and at the
scheduled humane kill.
CALCULATION OF RESULTS
32. Results for each treatment group are expressed as the SI. When using the individual animal approach, the SI is
derived by dividing the mean DPM/mouse within each test substance group, and the PC group, by the mean
DPM/mouse for the solvent/VC group. The average SI for the VCs is then one. When using the pooled treatment
group approach, the SI is obtained by dividing the pooled radioactive incorporation for each treatment group by
the incorporation of the pooled VC group; this yields a mean SI.
33. The decision process regards a result as positive when SI ≥ 3. However, the strength of the dose-response, the
statistical significance and the consistency of the solvent/vehicle and PC responses may also be used when
determining whether a borderline result is declared positive (4) (5) (6).
34. If it is necessary to clarify the results obtained, consideration should be given to various properties of the test
substance, including whether it has a structural relationship to known skin sensitisers, whether it causes excessive
local skin irritation in the mouse, and the nature of the dose-response relationship seen. These and other
considerations are discussed in detail elsewhere (7).
35. Collecting radioactivity data at the level of the individual mouse will enable a statistical analysis for presence and
degree of dose-response relationship in the data. Any statistical assessment could include an evaluation of the
dose-response relationship as well as suitably adjusted comparisons of test groups (e.g. pair-wise dosed group
versus concurrent VC comparisons). Statistical analyses may include, e.g. linear regression or William’s test to
assess dose-response trends, and Dunnett’s test for pair-wise comparisons. In choosing an appropriate method of
statistical analysis, the investigator should maintain an awareness of possible inequalities of variances and other
related problems that may necessitate a data transformation or a non-parametric statistical analysis. In any case
the investigator may need to carry out SI calculations and statistical analyses with and without certain data points
(sometimes called “outliers”).
DATA AND REPORTING
Data
36. Data should be summarised in tabular form. When using the individual animal approach, show the individual
animal DPM values, the group mean DPM/animal, its associated error term (e.g. SD, SEM), and the mean SI for
each dose group compared against the concurrent VC group. When using the pooled treatment group approach,
show the mean/median DPM and the mean SI for each dose group compared against the concurrent VC group.
Test report
37. The test report should contain the following information:
Test and control substances:
— identification data (e.g. CAS and EC numbers, if available; source; purity; known impurities; lot number);
— physical nature and physicochemical properties (e.g. volatility, stability, solubility);

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— if mixture, composition and relative percentages of components;
Solvent/vehicle:
— identification data (purity; concentration, where appropriate; volume used);
— justification for choice of vehicle;
Test animals:
— source of CBA mice;
— microbiological status of the animals, when known;
— number and age of animals;
— source of animals, housing conditions, diet, etc.;
Test conditions:
— details of test substance preparation and application;
— justification for dose selection (including results from pre-screen test, if conducted);
— vehicle and test substance concentrations used, and total amount of test substance applied;
— details of food and water quality (including diet type/source, water source);
— details of treatment and sampling schedules;
— methods for measurement of toxicity;
— criteria for considering studies as positive or negative;
— details of any protocol deviations and an explanation on how the deviation affects the study design and
results;
Reliability check:
— summary of results of latest reliability check, including information on test substance, concentration and
vehicle used;
— concurrent and/or historical PC and concurrent NC data for testing laboratory;
— if a concurrent PC was not included, the date and laboratory report for the most recent periodic PC and a
report detailing the historical PC data for the laboratory justifying the basis for not conducting a concurrent
PC;
Results:
— individual weights of mice at start of dosing and at scheduled kill; as well as mean and associated error term
(e.g. SD, SEM) for each treatment group;
— time course of onset and signs of toxicity, including dermal irritation at site of administration, if any, for each
animal;
— a table of individual mouse (individual animal approach) or mean/median (pooled treatment group approach)
DPM values and SI values for each treatment group;

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— mean and associated error term (e.g. SD, SEM) for DPM/mouse for each treatment group and the results of
outlier analysis for each treatment group when using the individual animal approach;
— calculated SI and an appropriate measure of variability that takes into account the inter-animal variability in
both the test substance and control groups when using the individual animal approach;
— dose-response relationship;
— statistical analyses, where appropriate;
Discussion of results:
— a brief commentary on the results, the dose-response analysis, and statistical analyses, where appropriate, with
a conclusion as to whether the test substance should be considered a skin sensitiser.
LITERATURE
(1) OECD (2002), Skin Sensitisation: Local Lymph Node Assay. OECD Guideline for the Testing of Chemicals
No 429, Paris. Available at: [http://www.oecd.org/env/testguidelines]
(2) Kimber, I. and Basketter, D.A. (1992), The murine local lymph node assay; collaborative studies and new
directions: A commentary, Food Chem. Toxicol., 30, 165-169.
(3) Kimber, I., Dearman, R.J., Scholes, E.W. and Basketter, D.A. (1994), The local lymph node assay: developments
and applications, Toxicol., 93, 13-31.
(4) Kimber, I., Hilton, J., Dearman, R.J., Gerberick, G.F., Ryan, C.A., Basketter, D.A., Lea, L., House, R.V., Ladies, G.S.,
Loveless, S.E. and Hastings, K.L. (1998), Assessment of the skin sensitisation potential of topical medicaments
using the local lymph node assay: An interlaboratory exercise, J. Toxicol. Environ. Health, 53, 563-79.
(5) Chamberlain, M. and Basketter, D.A. (1996), The local lymph node assay: status of validation, Food Chem. Toxicol.,
34, 999-1002.
(6) Basketter, D.A., Gerberick, G.F., Kimber, I. and Loveless, S.E. (1996), The local lymph node assay: A viable
alternative to currently accepted skin sensitisation tests, Food Chem. Toxicol., 34, 985-997.
(7) Basketter, D.A., Gerberick, G.F. and Kimber, I. (1998), Strategies for identifying false positive responses in
predictive sensitisation tests, Food Chem. Toxicol., 36, 327-33.
(8) Van Och, F.M.M., Slob, W., De Jong, W.H., Vandebriel, R.J. and Van Loveren, H. (2000), A quantitative method
for assessing the sensitising potency of low molecular weight chemicals using a local lymph node assay:
employment of a regression method that includes determination of uncertainty margins, Toxicol., 146, 49-59.
(9) Dean, J.H., Twerdok, L.E., Tice, R.R., Sailstad, D.M., Hattan, D.G., Stokes, W.S. (2001), ICCVAM evaluation of the
murine local lymph node assay: II. Conclusions and recommendations of an independent scientific peer review
panel, Reg. Toxicol. Pharmacol, 34: 258-273.
(10) Haneke, K.E., Tice, R.R., Carson, B.L., Margolin, B.H., Stokes, W.S. (2001), ICCVAM evaluation of the murine local
lymph node assay: III. Data analyses completed by the national toxicology program interagency center for the
evaluation of alternative toxicological methods, Reg. Toxicol. Pharmacol, 34, 274-286.
(11) Sailstad, D.M., Hattan, D., Hill, R.N., Stokes, W.S. (2001), ICCVAM evaluation of the murine local lymph node
assay: I. The ICCVAM review process, Reg. Toxicol. Pharmacol, 34: 249-257.
(12) ICCVAM (2009), Recommended Performance Standards: Murine Local Lymph Node Assay, NIH Publication
Number 09-7357, Research Triangle Park, NC: National Institute of Environmental Health Sciences. Available
at: [http://iccvam.niehs.nih.gov/docs/immunotox_docs/llna-ps/LLNAPerfStds.pdf]
(13) OECD (1992), Skin Sensitisation. OECD Guideline for Testing of Chemicals No 406, OECD, Paris. Available at:
[http://www.oecd.org/env/testguidelines]

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(14) OECD (2005), Guidance Document on the Validation and International Acceptance of New or Updated Test Methods for
Hazard Assessment, Environment, Health and Safety Monograph, Series on Testing and Assessment No 34, ENV/
JM/MONO(2005)14, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]
(15) Dearman, R.J., Hilton, J., Evans, P., Harvey, P., Basketter, D.A. and Kimber, I. (1998), Temporal stability of local
lymph node assay responses to hexyl cinnamic aldehyde, J. Appl. Toxicol., 18, 281-284.
(16) Kimber, I., Dearman, R.J., Betts, C.J., Gerberick, G.F., Ryan, C.A., Kern, P.S., Patlewicz, G.Y. and Basketter, D.A.
(2006), The local lymph node assay and skin sensitisation: a cut-down screen to reduce animal requirements?
Contact Dermatitis, 54, 181-185.
(17) ESAC (2007), Statement on the Reduced Local Lymph Node Assay (rLLNA), European Commission Directorate-
General, Joint Research Centre, Institute for Health and Consumer Protection, European Centre for the Validation
of Alternative Methods, April 2007. Available at: [http://ecvam.jrc.it/ft_doc/ESAC26_statement_rLLNA_
20070525-1.pdf]
(18) ICCVAM (2009), The Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM)
Test Method Evaluation Report. The Reduced Murine Local Lymph Node Assay: An Alternative Test Method
Using Fewer Animals to Assess the Allergic Contact Dermatitis Potential of Chemicals and Products, NIH
Publication Number 09-6439, Research Triangle Park, NC: National Institute of Environmental Health
Sciences. Available at: [http://iccvam.niehs.nih.gov/]
(19) ICCVAM (1999), The Murine Local Lymph Node Assay: A Test Method for Assessing the Allergic Contact
Dermatitis Potential of Chemicals/Compounds, The Results of an Independent Peer Review Evaluation Coor
dinated by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and the
National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods
(NICEATM), NIH Publication No 99-4494, Research Triangle Park, NC: National Institute of Environmental
Health Sciences. Available at: [http://iccvam.niehs.nih.gov/docs/immunotox_docs/llna/llnarep.pdf]
(20) Kreiling, R., Hollnagel, H.M., Hareng, L., Eigler, L., Lee, M.S., Griem, P., Dreessen, B., Kleber, M., Albrecht, A.,
Garcia, C. and Wendel, A. (2008), Comparison of the skin sensitising potential of unsaturated compounds as
assessed by the murine local lymph node assay (LLNA) and the guinea pig maximization test (GPMT), Food
Chem. Toxicol., 46, 1896-1904.
(21) Basketter, D., Ball, N., Cagen, S., Carrilo, J.C., Certa, H., Eigler, D., Garcia, C., Esch, H., Graham, C., Haux, C.,
Kreiling, R. and Mehling, A. (2009), Application of a weight of evidence approach to assessing discordant
sensitisation datasets: implications for REACH, Reg. Toxicol. Pharmacol., 55, 90-96.
(22) ICCVAM (2009), ICCVAM Test Method Evaluation Report. Assessment of the Validity of the LLNA for Testing
Pesticide Formulations and Other Products, Metals, and Substances in Aqueous Solutions, NIH Publication
Number 10-7512, Research Triangle Park, NC: National Institute of Environmental Health Sciences, Available
at: [http://iccvam.niehs.nih.gov/]
(23) ILAR (1996), Institute of Laboratory Animal Research (ILAR) Guide for the Care and Use of Laboratory Animals,
7th ed. Washington, DC: National Academies Press.
(24) McGarry, H.F. (2007), The murine local lymph node assay: regulatory and potency considerations under REACH,
Toxicol., 238, 71-89.
(25) OECD (2002), Acute Dermal Irritation/Corrosion. OECD Guideline for Testing of Chemicals No 404, Paris,
France. Available at: [http://www.oecd.org/document/40/0,3343,en_2649_34377_37051368_1_1_1_1,00.html]
(26) Reeder, M.K., Broomhead, Y.L., DiDonato, L. and DeGeorge, G.L. (2007), Use of an enhanced local lymph node
assay to correctly classify irritants and false positive substances, Toxicologist, 96, 235.
(27) ICCVAM (2009), Non-radioactive Murine Local Lymph Node Assay: Flow Cytometry Test Method Protocol
(LLNA: BrdU-FC) Revised Draft Background Review Document, Research Triangle Park, NC: National Institute
of Environmental Health Sciences. Available at: [http://iccvam.niehs.nih.gov/methods/immunotox/fcLLNA/
BRDcomplete.pdf]

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(28) Hayes, B.B., Gerber, P.C., Griffey, S.S. and Meade, B.J. (1998), Contact hypersensitivity to dicyclohexylcarbodiimide
and diisopropylcarbodiimide in female B6C3F1 mice, Drug. Chem. Toxicol., 21, 195-206.
(29) Homey, B., von Schilling, C., Blumel, J., Schuppe, H.C., Ruzicka, T., Ahr, H.J., Lehmann, P. and Vohr, V.W.
(1998), An integrated model for the differentiation of chemical-induced allergic and irritant skin reactions,
Toxicol. Appl. Pharmacol., 153, 83-94.
(30) Woolhiser, M.R., Hayes, B.B. and Meade, B.J. (1998), A combined murine local lymph node and irritancy assay to
predict sensitisation and irritancy potential of chemicals, Toxicol. Meth., 8, 245-256.
(31) Hayes, B.B. and Meade, B.J. (1999), Contact sensitivity to selected acrylate compounds in B6C3F1 mice: relative
potency, cross reactivity, and comparison of test methods, Drug. Chem. Toxicol., 22, 491-506.
(32) Ehling, G., Hecht, M., Heusener, A., Huesler, J., Gamer, A.O., van Loveren, H., Maurer, T., Riecke, K., Ullmann, L.,
Ulrich, P., Vandebriel, R. and Vohr, H.W. (2005), A European inter-laboratory validation of alternative endpoints
of the murine local lymph node assay: first round. Toxicol., 212, 60-68.
(33) Vohr, H.W. and Ahr, H.J. (2005), The local lymph node assay being too sensitive? Arch. Toxicol., 79, 721-728.
(34) Patterson, R.M., Noga, E. and Germolec, D. (2007), Lack of evidence for contact sensitisation by Pfiesteria extract,
Environ. Health Perspect., 115, 1023-1028.
(35) OECD (1987), Acute Dermal Toxicity, OECD Guideline for Testing of Chemicals No 402, Paris, France. Available
at: [http://www.oecd.org/env/testguidelines]
(36) ICCVAM (2009), Report on the ICCVAM-NICEATM/ECVAM/JaCVAM Scientific Workshop on Acute Chemical
Safety Testing: Advancing In Vitro Approaches and Humane Endpoints for Systemic Toxicity Evaluations.
Research Triangle Park, NC: National Institute of Environmental Health Sciences, Available at: [http://iccvam.
niehs.nih.gov/methods/acutetox/Tox_workshop.htm]
(37) OECD (2000), Guidance Document on the Recognition, Assessment and Use of Clinical Signs as Humane Endpoints for
Experimental Animals Used in Safety Evaluation, Environmental Health and Safety Monograph, Series on Testing and
Assessment No 19, ENV/JM/MONO(2000)7, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]
Appendix 1
Performance standards for assessment of proposed similar or modified llna test methods for skin sensitisation
INTRODUCTION
1. The purpose of Performance Standards (PS) is to communicate the basis by which new test methods, both
proprietary (i.e. copyrighted, trademarked, registered) and non-proprietary can be determined to have sufficient
accuracy and reliability for specific testing purposes. These PS, based on validated and accepted test methods, can be
used to evaluate the reliability and accuracy of other similar methods (colloquially referred to as “me-too” tests) that
are based on similar scientific principles and measure or predict the same biological or toxic effect (14).
2. Prior to adoption of modified methods (i.e. proposed potential improvements to an approved test method), there
should be an evaluation to determine the effect of the proposed changes on the test’s performance and the extent
to which such changes affect the information available for the other components of the validation process.
Depending on the number and nature of the proposed changes, the generated data and supporting documentation
for those changes, they should either be subjected to the same validation process as described for a new test, or, if
appropriate, to a limited assessment of reliability and relevance using established PS (14).
3. Similar or modified methods proposed for use under this TM should be evaluated to determine their reliability and
accuracy using chemicals representing the full range of the LLNA scores. To avoid unwarranted animal use, it is
strongly recommended that model developers consult the appropriate authorities before starting validation studies
in accordance with the PS and guidance provided in this TM.
4. These PS are based on the US-ICCVAM, EC-ECVAM and Japanese-JaCVAM harmonised PS (12), for evaluating the
validity of similar or modified versions of the LLNA. The PS consists of essential test method components,
recommended reference chemicals and standards for accuracy and reliability that the proposed method should
meet or exceed.

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I. Essential test method components
5. To ensure that a similar or modified LLNA method is functionally and mechanistically analogous to the LLNA and
measures the same biological effect, the following components should be included in the test method protocol:
— The test substance should be applied topically to both ears of the mouse;
— Lymphocyte proliferation should be measured in the lymph nodes draining from the site of test substance
application;
— Lymphocyte proliferation should be measured during the induction phase of skin sensitisation;
— For test substances, the highest dose selected should be the maximum concentration that does not induce
systemic toxicity and/or excessive local skin irritation in the mouse. For positive reference chemicals, the highest
dose should be at least as high as the LLNA EC3 values of the corresponding reference chemicals (see Table 1)
without producing systemic toxicity and/or excessive local skin irritation in the mouse;
— A concurrent VC should be included in each study and, where appropriate, a concurrent PC should also be
used;
— A minimum of four animals per dose group should be used;
— Either individual or pooled animal data may be collected.
If any of these criteria are not met, then these PS cannot be used for validation of the similar or modified method.
II. Minimum list of reference chemicals
6. The US-ICCVAM, EC-ECVAM and Japanese-JaCVAM harmonised PS (12) identified 18 minimum reference
chemicals that should be used and four optional reference chemicals (i.e. substances that produced either false
positive or false negative results in the LLNA, when compared to human and guinea pig results (B.6, or OECD Test
Guideline 406) (13), and therefore provide the opportunity to demonstrate equal to or better performance than the
LLNA) that are included in the LLNA PS. The selection criteria for identifying these chemicals were:
— The list of reference chemicals represented the types of substances typically tested for skin sensitisation potential
and the range of responses that the LLNA is capable of measuring or predicting;
— The substances had well-defined chemical structures;
— LLNA data from guinea pig tests (i.e. B.6; OECD Test Guideline 406) (13) and (where possible) data from
humans were available for each substance; and
— The substances were readily available from a commercial source.
The recommended reference chemicals are listed in Table 1. Studies using the proposed reference chemicals should
be evaluated in the vehicle with which they are listed in Table 1. In situations where a listed substance may not be
available, other substances that meet the selection criteria mentioned may be used, with adequate justification.

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Table 1
Recommended Reference chemicals for the LLNA PS.
Number Chemicals
(1 ) CAS
No Form Veh
(2 ) EC3
%
(3 ) N
(4 ) 0,5x-2,0x
EC3
Actual EC3
Range
LLNA vs GP
LLNA vs
Human
1 5-Chloro-2-methyl-4-isothiazolin-3-one
(CMI)/2-methyl-4-
26172-55-4/
Liq DMF 0,009
1 0,0045-0,018 NC +/+ +/+
EN
isothiazolin-3-one (MI) (5 )
2682-20-4

2 DNCB 97-00-7 Sol AOO 0,049 15 0,025-0,099 0,02-0,094 +/+ +/+
3 4-Phenylenediamine 106-50-3 Sol AOO 0,11
6 0,055-0,22 0,07-0,16 +/+ +/+
4 Cobalt
chloride 7646-79-9 Sol DMSO 0,6
2 0,3-1,2 0,4-0,8 +/+ +/+
5 Isoeugenol 97-54-1 Liq AOO 1,5 47 0,77-3,1 0,5-3,3 +/+ +/+
Off
icial
6 2-Mercaptobenzothiazole 149-30-4 Sol DMF 1,7
1 0,85-3,4 NC +/+ +/+
Jour
nal
7 Citral 5392-40-5 Liq AOO 9,2
6 4,6-18,3 5,1-13 +/+ +/+
of
the
8 HCA 101-86-0 Liq AOO 9,7 21 4,8-19,5 4,4-14,7 +/+ +/+
European
9 Eugenol 97-53-0 Liq AOO 10,1 11 5,05-20,2 4,9-15 +/+ +/+
10 Phenyl
benzoate 93-99-2 Sol AOO 13,6
3 6,8-27,2 1,2-20 +/+ +/+
Union
11 Cinnamic
alcohol 104-54-1 Sol AOO 21
1 10,5-42 NC +/+ +/+
12 Imidazolidinyl
urea 39236-46-9 Sol DMF 24
1 12-48 NC +/+ +/+
13 Methyl
methacrylate 80-62-6 Liq AOO 90
1 45-100 NC +/+ +/+
14 Chlorobenzene 108-90-7 Liq AOO 25
1 NA NA –/– –/
(*)
15 Isopropanol 67-63-0 Liq AOO 50
1 NA NA –/– –/+
16 Lactic
acid 50-21-5 Liq DMSO 25
1 NA NA –/– –/
(*)
20.7.2012
17 Methyl
salicylate 119-36-8 Liq AOO 20
9 NA NA –/– –/–
18 Salicylic
acid 69-72-7 Sol AOO 25
1 NA NA –/– –/–

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Number Chemicals
(1 ) CAS
No Form Veh
(2 ) EC3
%
(3 ) N
(4 ) 0,5x-2,0x
EC3
Actual EC3
Range
LLNA vs GP
LLNA vs
Human
Optional Substances to Demonstrate Improved Performance Relative to the LLNA
19 Sodium
lauryl
sulphate 151-21-3 Sol DMF 8,1
5 4,05-16,2 1,5-17,1 +/– +/–
EN
20 Ethylene
glycol
dimethacrylate 97-90-5 Liq MEK 28
1 14-56 NC +/– +/+

21 Xylene 1330-20-7 Liq AOO 95,8
1 47,9-100 NC +/
(**) +/–
22 Nickel
chloride 7718-54-9 Sol DMSO
5
2 NA NA –/+ –/+
Abbreviations: AOO = acetone: olive oil (4:1, v/v); CAS No = Chemical Abstracts Service Number; DMF = N,N-dimethylformamide; DMSO = dimethyl sulfoxide; DNCB = 2,4-dinitrochlorobenzene; EC3 = estimated concentration needed to
produce a stimulation index of 3; GP = guinea pig test result (i.e. B.6 or OECD Test Guideline 406) (13); HCA = hexyl cinnamic aldehyde; Liq = liquid; LLNA = murine local lymph node assay result (i.e. B.42 or OECD Test Guideline 429) (1);
MEK = methyl ethyl ketone; NA = not applicable since stimulation index < 3; NC = not calculated since data was obtained from a single study; Sol = solid; Veh = test vehicle.
(*) Presumed to be a non-sensitiser in humans based on the fact that no clinical patch test results were located, it is not included as a patch test kit allergen, and no case reports of human sensitisation were located.
(**) GP data not available.
(1 ) Chemicals should be prepared daily unless stability data demonstrate the acceptability of storage.
icial
(2 ) Because of the potential impact of different vehicles on the performance of the LLNA, the recommended vehicle for each reference chemical should be used (24) (32).
(3 ) Mean value where more than one EC3 value was available. For negative substances (i.e. with stimulation index < 3, the highest concentration tested is provided).
Jour
(4 ) Number of LLNA studies from which data were obtained.
(5 ) Commercially available as Kathon CG (CAS No 55965-84-9), which is a 3:1 mixture of CMI and MI. The relative concentrations of each component range from 1,1 % to 1,25 % (CMI) and 0,3 % to 0,45 % (MI). The inactive components
nal
are magnesium salts (21,5 % to 24 %) and copper nitrate (0,15 % to 0,17 %), with the remaining formulation 74 % to 77 % water. Kathon CG is readily available through Sigma-Aldrich and Rohm and Haas (now Dow Chemical
of
Corporation).
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III. Defined reliability and accuracy standards
7. The accuracy of a similar or modified LLNA method should meet or exceed that of the LLNA PS when it is
evaluated using the 18 minimum reference chemicals that should be used. The new or modified method should
result in the correct classification based on a “yes/no” decision. However, the new or modified method might not
correctly classify all of the minimum reference chemicals that should be used. If, for example, one of the weak
sensitisers were misclassified, a rationale for the misclassification and appropriate additional data (e.g. test results
that provide correct classifications for other substances with physical, chemical, and sensitising properties similar to
those of the misclassified reference chemical) could be considered to demonstrate equivalent performance. Under
such circumstances, the validation status of the new or modified LLNA test method would be evaluated on a case-
by-case basis.
Intra-laboratory reproducibility
8. To determine intra-laboratory reproducibility, a new or modified LLNA method should be assessed using a
sensitising substance that is well characterised in the LLNA. Therefore, the LLNA PS are based on the variability
of results from repeated tests of hexyl cinnamic aldehyde (HCA). To assess intra-laboratory reliability, threshold
estimated concentration (ECt) values for HCA should be derived on four separate occasions with at least one week
between tests. Acceptable intra-laboratory reproducibility is indicated by a laboratory’s ability to obtain, in each
HCA test, ECt values between 5 % and 20 %, which represents the range of 0,5-2,0 times the mean EC3 specified
for HCA (10 %) in the LLNA (see Table 1).
Inter-laboratory reproducibility
9. Inter-laboratory reproducibility of a new or modified LLNA method should be assessed using two sensitising
substances that are well characterised in the LLNA. The LLNA PS are based on the variability of results from
tests of HCA and 2,4-dinitrochlorobenzene (DNCB) in different laboratories. ECt values should be derived indepen
dently from a single study conducted in at least three separate laboratories. To demonstrate acceptable inter-
laboratory reproducibility, each laboratory should obtain ECt values of 5 % to 20 % for HCA and 0,025 % to
0,1 % for DNCB, which represents the range of 0,5-2,0 times the mean EC3 concentrations specified for HCA
(10 %) and DNCB (0,05 %), respectively, in the LLNA (see Table 1).
Appendix 2
Definitions
Accuracy: The closeness of agreement between test method results and accepted reference values. It is a measure of test
method performance and one aspect of relevance. The term is often used interchangeably with “concordance” to mean
the proportion of correct outcomes of a test method (14).
Benchmark substance: A sensitising or non-sensitising substance used as a standard for comparison to a test substance. A
benchmark substance should have the following properties: (i) consistent and reliable source(s); (ii) structural and
functional similarity to the class of substances being tested; (iii) known physicochemical characteristics; (iv) supporting
data on known effects; and (v) known potency in the range of the desired response.
Estimated concentration threshold (ECt): Estimated concentration of a test substance needed to produce a stimulation
index that is indicative of a positive response.
Estimated concentration three (EC3): Estimated concentration of a test substance needed to produce a stimulation index of
three.
False negative: A test substance incorrectly identified as negative or non-active by a test method, when in fact it is
positive or active.
False positive: A test substance incorrectly identified as positive or active by a test, when in fact it is negative or non-
active.
Hazard: The potential for an adverse health or ecological effect. The adverse effect is manifested only if there is an
exposure of sufficient level.
Inter-laboratory reproducibility: A measure of the extent to which different qualified laboratories, using the same protocol
and testing the same test substances, can produce qualitatively and quantitatively similar results. Inter-laboratory
reproducibility is determined during the pre-validation and validation processes, and indicates the extent to which a
test can be successfully transferred between laboratories, also referred to as between-laboratory reproducibility (14).
Intra-laboratory reproducibility: A determination of the extent that qualified people within the same laboratory can
successfully replicate results using a specific protocol at different times. Also referred to as within-laboratory repro
ducibility (14).

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Me-too test: A colloquial expression for a test method that is structurally and functionally similar to a validated and
accepted reference test method. Such a test method would be a candidate for catch-up validation. Interchangeably used
with similar test method (14).
Outlier: An outlier is an observation that is markedly different from other values in a random sample from a
population.
Performance standards (PS): Standards, based on a validated test method, that provide a basis for evaluating the
comparability of a proposed test method that is functionally and mechanistically similar. Included are: (i) essential
test method components; (ii) a minimum list of Reference Chemicals selected from among the chemicals used to
demonstrate the acceptable performance of the validated test method; and (iii) the similar levels of accuracy and
reliability, based on what was obtained for the validated test method, that the proposed test method should demon
strate when evaluated using the minimum list of Reference Chemicals (14).
Proprietary test method: A test method for which manufacture and distribution is restricted by patents, copyrights,
trademarks, etc.
Quality assurance: A management process by which adherence to laboratory testing standards, requirements, and record
keeping procedures, and the accuracy of data transfer, are assessed by individuals who are independent from those
performing the testing.
Reference chemicals: Chemicals selected for use in the validation process, for which responses in the in vitro or in vivo
reference test system or the species of interest are already known. These chemicals should be representative of the
classes of chemicals for which the test method is expected to be used, and should represent the full range of responses
that may be expected from the chemicals for which it may be used, from strong, to weak, to negative. Different sets of
reference chemicals may be required for the different stages of the validation process, and for different test methods
and test uses (14).
Relevance: Description of relationship of the test to the effect of interest and whether it is meaningful and useful for a
particular purpose. It is the extent to which the test correctly measures or predicts the biological effect of interest.
Relevance incorporates consideration of the accuracy (concordance) of a test method (14).
Reliability: Measures of the extent that a test method can be performed reproducibly within and between laboratories
over time, when performed using the same protocol. It is assessed by calculating intra- and inter-laboratory repro
ducibility (14).
Skin sensitisation: An immunological process that results when a susceptible individual is exposed topically to an
inducing chemical allergen, which provokes a cutaneous immune response that can lead to the development of contact
sensitisation.
Stimulation Index (SI): A value calculated to assess the skin sensitisation potential of a test substance that is the ratio of
the proliferation in treated groups to that in the concurrent vehicle control group.
Test substance (also referred to as test chemical): Any substance or mixture tested using this TM.
Validated test method: A test method for which validation studies have been completed to determine the relevance
(including accuracy) and reliability for a specific purpose. It is important to note that a validated test method may not
have sufficient performance in terms of accuracy and reliability to be found acceptable for the proposed purpose (14).’
2. Chapter B.46 is replaced by the following:
‘B.46. IN VITRO SKIN IRRITATION: RECONSTRUCTED HUMAN EPIDERMIS TEST METHOD
INTRODUCTION
1. Skin irritation refers to the production of reversible damage to the skin following the application of a test
chemical for up to 4 hours (as defined by the United Nations (UN) Globally Harmonised System of Classification
and Labelling of Chemicals (GHS) and Regulation (EC) No 1272/2008 of the European Parliament and of the
Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures (1) (3)). This
Test Method (TM) provides an in vitro procedure that may be used for the hazard identification of irritant
chemicals (substances and mixtures) in accordance with UN GHS and EU CLP Category 2 (1) (2) (3). In the
EU and other regions, that have not adopted the optional UN GHS Category 3 (mild irritants), this TM can also be
used to identify non-classified chemicals, i.e. UN GHS and EU CLP “No Category” (1) (3). This TM may be used to
determine the skin irritancy of chemicals as a stand-alone replacement test for in vivo skin irritation testing within
a tiered testing strategy (4 and Chapter B.4 in this Annex).

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2. The
assessment
of
skin
irritation
has
typically
involved
the
use
of
laboratory
animals
(OECD
Test
Guideline
404;
Chapter B.4 in this Annex) (4). In relation to animal welfare concerns, B.4 was revised in 2004 allowing for the
determination of skin corrosion/irritation by applying a tiered testing strategy, using validated in vitro or ex vivo
test methods, thus avoiding pain and suffering of animals. Three validated in vitro test methods have been adopted
as OECD Test Guidelines 430, 431 and 435 (5) (6) (7) and two of them as Chapters B.40 and B.40a of this
Annex, to be used for the corrosivity part of the tiered testing strategy of B.4 or OECD Test Guideline 404 (4).
3. This TM addresses the human health endpoint skin irritation. It is based on reconstructed human epidermis (RhE),
which in its overall design (the use of human derived non-transformed epidermis keratinocytes as cell source and
use of representative tissue and cytoarchitecture) closely mimics the biochemical and physiological properties of
the upper parts of the human skin, i.e. the epidermis. This TM also includes a set of Performance Standards (PS)
(Appendix 2) for the assessment of similar and modified RhE-based methods developed by EC-ECVAM (8), in
accordance with the principles of OECD Guidance Document No 34 (9).
4. There are three validated methods that adhere to this TM. Prevalidation, optimisation and validation studies have
been completed for an in vitro method (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20), using a RhE model,
commercially available as EpiSkin TM (designated the Validated Reference Method — VRM). Two other commer
cially available in vitro skin irritation RhE methods have shown similar results to the VRM according to PS-based
validation (21), and these are the EpiDerm TM SIT (EPI-200) and the SkinEthic TM RHE methods (22).
5. Before a proposed
similar
or modified in vitro RhE method other than the VRM, EpiDerm TM SIT (EPI-200) or
SkinEthic TM RHE methods can be used for regulatory purposes, its reliability, relevance (accuracy), and limitations
for its proposed use should be determined in order to ensure that it can be regarded as similar to that of the VRM,
in accordance with the requirements of the PS set out in this TM (Appendix 2). Moreover, it is recommended to
consult the OECD Explanatory Background Document on in vitro skin irritation testing before developing and
validating a similar or modified in vitro RhE method and submitting it for regulatory adoption (23).
DEFINITIONS
6. Definitions
used
are
provided
in
Appendix
1.
INITIAL CONSIDERATIONS AND LIMITATIONS
7. A limitation of the TM, as demonstrated by the validation study (16), is that it does not allow the classification of
chemicals to the optional UN GHS Category 3 (mild irritants) (1). When used as a partial replacement test, follow-
up in vivo testing may be required to fully characterise skin irritation potential (4 and Chapter B.4 of this Annex).
It is recognised that the use of human skin is subject to national and international ethical considerations and
conditions.
8. This
TM
addresses
the in vitro skin irritation component of the tiered testing strategy of B.4 (OECD Test Guideline
404) on dermal corrosion/irritation (4). While this TM does not provide adequate information on skin corrosion,
it should be noted that B.40a (OECD Test Guideline 431) on skin corrosion is based on the same RhE test system,
though using another protocol (Chapter B.40a). This method is based on RhE-models using human keratinocytes,
which therefore represent in vitro the target organ of the species of interest. It moreover directly covers the initial
step of the inflammatory cascade/mechanism of action (cell damage and tissue damage resulting in localised
trauma) that occurs during irritation in vivo. A wide range of chemicals has been tested in the validation
underlying this TM and the empirical database of the validation study amounted to 58 chemicals in total (16)
(18) (23). This is applicable to solids, liquids, semi-solids and waxes. The liquids may be aqueous or non-aqueous;
solids may be soluble or insoluble in water. Whenever possible, solids should be ground to a fine powder before
application; no other pre-treatment of the sample is required. Gases and aerosols have not been assessed yet in a
validation study (24). While it is conceivable that these can be tested using RhE technology, the current TM does
not allow testing of gases and aerosols. It should also be noted that highly coloured chemicals may interfere with
the cell viability measurements and need the use of adapted controls for corrections (see paragraphs 24-26).
9. A single testing run composed of three replicate tissues should be sufficient for a test chemical when the
classification is unequivocal. However, in cases of borderline results, such as non-concordant replicate
measurements and/or mean percent viability equal to 50 ± 5 %, a second run should be considered, as well as
a third one in case of discordant results between the first two runs.
PRINCIPLE OF THE TEST
10. The test chemical is applied topically to a three-dimensional RhE model, comprised of non-transformed human-
derived epidermal keratinocytes, which have been cultured to form a multilayered, highly differentiated model of
the human epidermis. It consists of organised basal, spinous and granular layers, and a multilayered stratum corneum
containing intercellular lamellar lipid layers representing main lipid classes analogous to those found in vivo.

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11. Chemical-induced skin irritation, manifested by erythema and oedema, is the result of a cascade of events
beginning with penetration of the stratum corneum and damage to the underlying layers of keratinocytes. The
dying keratinocytes release mediators that begin the inflammatory cascade which acts on the cells in the dermis,
particularly the stromal and endothelial cells. It is the dilatation and increased permeability of the endothelial cells
that produce the observed erythema and oedema (24). The RhE-based methods measure the initiating events in
the cascade.
12. Cell viability in RhE models is measured by enzymatic conversion of the vital dye MTT (3-(4,5-Dimethylthiazol-2-
yl)-2,5-diphenyltetrazolium bromide, Thiazolyl blue); CAS number 298-93-1 into a blue formazan salt that is
quantitatively measured after extraction from tissues (25). Irritant chemicals are identified by their ability to
decrease cell viability below defined threshold levels (i.e. ≤ 50 %, for UN GHS/EU CLP Category 2). Depending
on the regulatory framework in which the results of this TM are used, chemicals that produce cell viabilities above
the defined threshold level, may be considered non-irritants (i.e. > 50 %, No Category).
DEMONSTRATION OF PROFICIENCY
13. Prior to routine use of any of the three validated methods that adhere to this TM, laboratories should demonstrate
technical proficiency, using the ten Reference Chemicals listed in Table 1. For similar methods developed under
this TM or for modifications of any of the three validated methods, the PS requirements described in Appendix 2
of this TM should be met prior to using the method for regulatory testing.
14. As part of the proficiency exercise, it is recommended that the user verifies the barrier properties of the tissues
after receipt as specified by the RhE model producer. This is particularly important if tissues are shipped over long
distance/time periods. Once a method has been successfully established and proficiency in its use has been
demonstrated, such verification will not be necessary on a routine basis. However, when using a method routinely,
it is recommended to continue to assess the barrier properties in regular intervals.
Table 1
Reference Chemicals ( 1 )
Chemical CAS
NR In
vivo score ( 2 ) Physical
state UN
GHS/EU
CLP
Category
naphthalene acetic acid 86-87-3
0 Solid No
Cat.
isopropanol 67-63-0 0,3 Liquid No
Cat.
methyl stearate 112-61-8
1 Solid No
Cat.
heptyl butyrate 5870-93-9 1,7 Liquid No
Cat.
(Optional Cat. 3) ( 3 ), ( 4 )
hexyl salicylate 6259-76-3
2 Liquid No
Cat.
(Optional Cat. 3) ( 3 ), ( 4 )
cyclamen aldehyde 103-95-7 2,3 Liquid Cat.
2
1-bromohexane 111-25-1 2,7 Liquid Cat.
2
potassium hydroxide (5 % aq.) 1310-58-3
3 Liquid Cat.
2
1-methyl-3-phenyl-1-piperazine 5271-27-2 3,3 Solid Cat.
2
Heptanal 111-71-7 3,4 Liquid Cat.
2
( 1 ) These Reference Chemicals are a subset of the Reference Chemicals used in the validation study.
( 2 ) In vivo score in accordance with B.4 and OECD Test Guideline 404 (4).
( 3 ) Under this Test Method, the UN GHS optional Category 3 (mild irritants) (1) is considered as No Category.
( 4 ) The UN GHS optional Category3 is not applicable under the EU CLP.

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PROCEDURE
15. The following is a description of the components and procedures of a RhE method for skin irritation assessment.
A RhE model should be reconstructed, and can be in-house-prepared or obtained commercially. Standard
Operating Procedures (SOPs) for the EpiSkin TM , EpiDerm TM SIT (EPI-200) and SkinEthic TM RHE are available
(26) (27) (28). Testing should be performed according to the following:
RhE Test Method Components
General conditions
16. Non-transformed human keratinocytes should be used to reconstruct the epithelium. Multiple layers of viable
epithelial cells (basal layer, stratum spinosum, stratum granulosum) should be present under a functional stratum
corneum. Stratum corneum should be multilayered containing the essential lipid profile to produce a functional
barrier with robustness to resist rapid penetration of cytotoxic marker chemicals, e.g. sodium dodecyl sulphate
(SDS) or Triton X-100. The barrier function should be demonstrated and may be assessed either by determination
of the concentration at which a marker chemical reduces the viability of the tissues by 50 % (IC 50 ) after a fixed
exposure time, or by determination of the exposure time required to reduce cell viability by 50 % (ET 50 ) upon
application of the marker chemical at a specified, fixed concentration. The containment properties of the RhE
model should prevent the passage of material around the stratum corneum to the viable tissue, which would lead to
poor modelling of skin exposure. The RhE model should be free of contamination by bacteria, viruses, myco
plasma, or fungi.
Functional conditions
Viability
17. The assay used for determining the magnitude of viability is the MTT-assay (25). The RhE model users should
ensure that each batch of the RhE model used meets defined criteria for the negative control (NC). The optical
density (OD) of the extraction solvent alone should be sufficiently small, i.e. OD< 0,1. An acceptability range
(upper and lower limit) for the negative control OD values (in the Skin Irritation Test Method conditions) are
established by the RhE model developer/supplier, and the acceptability ranges for the 3 validated methods are
given in Table 2. It should be documented that the tissues treated with NC are stable in culture (provide similar
viability measurements) for the duration of the test exposure period.
Table 2
Acceptability ranges for negative control OD values
Lower acceptance limit Upper
acceptance
limit
EpiSkin TM (SM)
≥ 0,6
≤ 1,5
EpiDerm TM SIT (EPI-200)
≥ 1,0
≤ 2,5
SkinEthic TM RHE
≥ 1,2
≤ 2,5
Barrier function
18. The stratum corneum and its lipid composition should be sufficient to resist the rapid penetration of cytotoxic
marker chemicals, e.g. SDS or Triton X-100, as estimated by IC 50 or ET 50 (Table 3).
Morphology
19. Histological examination of the RhE model should be performed demonstrating human epidermis-like structure
(including multilayered stratum corneum).
Reproducibility
20. The results of the positive control chemical (PC) and negative controls (NC) of the test method should demon
strate reproducibility over time.

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Quality control (QC)
21. The RhE model developer/supplier should ensure and demonstrate that each batch of the RhE model used meets
defined production release criteria, among which those for viability (paragraph 17), barrier function (paragraph 18)
and morphology (paragraph 19) are the most relevant. These data should be provided to the method users, so that
they are able to include this information in the test report. An acceptability range (upper and lower limit) for the
IC 50 or the ET 50 should be established by the RhE model developer/supplier (or investigator when using an in-
house model). Only results produced with qualified tissues can be accepted for reliable prediction of irritation
classification. As an example, the acceptability ranges for the three validated methods are given in Table 3.
Table 3
Examples of QC batch release criteria
Lower acceptance limit Upper
acceptance
limit
EpiSkin TM (SM)
IC 50 = 1,0 mg/ml IC 50 = 3,0 mg/ml
(18 hours treatment with SDS) (26)
EpiDerm TM SIT (EPI-200)
ET 50 = 4,8 hr ET 50 = 8,7 hr
(1 % Triton X-100) (27)
SkinEthic TM RHE
ET 50 = 4,0 hr ET 50 = 9,0 hr
(1 % Triton X-100) (28)
Application of the Test and Control Chemicals
22. At least three replicates should be used for each test chemical and for the controls in each run. For liquids as well
as solids, sufficient amount of test chemical should be applied to uniformly cover the epidermis surface while
avoiding an infinite dose, i.e. a minimum of 25 μL/cm 2 or 25 mg/cm 2 should be used. For solids, the epidermis
surface should be moistened with deionised or distilled water before application, to improve contact between the
test chemical and the epidermis surface. Whenever possible, solids should be tested as a fine powder. At the end of
the exposure period, the test chemical should be carefully washed from the epidermis surface with aqueous buffer,
or 0,9 % NaCl. Depending on which of the three validated RhE methods is used, the exposure period varies
between 15 and 60 minutes, and the incubation temperature between 20 and 37 °C. These exposure periods and
temperatures are optimised for each RhE method and represent the different intrinsic properties of the methods,
for details, see the Standard Operating Procedures (SOPs) for the methods (26) (27) (28).
23. Concurrent NC and PC should be used in each run to demonstrate that viability (with the NC), barrier function
and resulting tissue sensitivity (with the PC) of the tissues are within a defined historical acceptance range. The
suggested PC is 5 % aqueous SDS. The suggested NC chemicals are water or phosphate buffered saline (PBS).
Cell Viability Measurements
24. The most important element of the test procedure is that viability measurements are not performed immediately
after the exposure to the test chemicals, but after a sufficiently long post-treatment incubation period of the rinsed
tissues in fresh medium. This period allows both for recovery from weak cytotoxic effects and for appearance of
clear cytotoxic effects. The test optimisation phase (11) (12) (13) (14) (15) demonstrated that a 42 hours post-
treatment incubation period was optimal.
25. The MTT assay is a validated quantitative method which should be used to measure cell viability under this TM. It
is compatible with use in a three-dimensional tissue construct. The tissue sample is placed in MTT solution of
appropriate concentration (e.g. 0,3-1 mg/mL) for 3 hours. The precipitated blue formazan product is then
extracted from the tissue using a solvent (e.g. isopropanol, acidic isopropanol), and the concentration of
formazan is measured by determining the OD at 570 nm using a filter band pass of maximum ± 30 nm.
26. Optical properties of the test chemical or its chemical action on the MTT may interfere with the assay leading to a
false estimate of viability (because the test chemical may prevent or reverse the colour generation as well as cause
it). This may occur when a specific test chemical is not completely removed from the tissue by rinsing or when it
penetrates the epidermis. If a test chemical acts directly on the MTT (MTT-reducer), is naturally coloured, or
becomes coloured during tissue treatment, additional controls should be used to detect and correct for test
chemical interference with the viability measurement technique. Detailed description of how to correct direct
MTT reduction and interferences by colouring agents is available in the SOPs for the three validated methods (26)
(27) (28).

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Acceptability Criteria
27. For each method using valid RhE model batches (see paragraph 21), tissues treated with the NC should exhibit OD
reflecting the quality of the tissues that followed shipment, receipt steps and all protocol processes. Control OD
values should not be below historically established boundaries. Similarly, tissues treated with the PC, i.e. 5 %
aqueous SDS, should reflect their ability to respond to an irritant chemical under the conditions of the TM(26)
(27) (28). Associated and appropriate measures of variability between tissue replicates should be defined (e.g. if
standard deviations (SD) are used they should be within the 1-sided 95 % tolerance interval calculated from
historical data; for the VRM SD < 18 %).
Interpretation of Results and Prediction Model
28. The OD values obtained with each test chemical can be used to calculate the percentage of viability normalised to
NC, which is set to 100 %. The cut-off value of percentage cell viability distinguishing irritant from non-classified
test chemicals and the statistical procedure(s) used to evaluate the results and identify irritant chemicals should be
clearly defined, documented, and proven to be appropriate. The cut-off values for the prediction of irritation are
given below:
— the test chemical is considered to be irritant to skin in accordance with UN GHS/EU CLP Category 2 if the
tissue viability after exposure and post-treatment incubation is less than or equal (≤) to 50 %.
— depending on the regulatory framework in which the results of this TM are used, the test chemical may be
considered to be non-irritant to skin in accordance with UN GHS/EU CLP No Category if the tissue viability
after exposure and post-treatment incubation is more than (>) 50 %.
DATA AND REPORTING
Data
29. For each run, data from individual replicate tissues (e.g. OD values and calculated percentage cell viability data for
each test chemical, including classification) should be reported in tabular form, including data from repeat
experiments as appropriate. In addition means ± SD for each run should be reported. Observed interactions
with MTT reagent and coloured test chemicals should be reported for each tested chemical.
Test Report
30. The test report should include the following information:
Test and Control Chemicals:
— Chemical name(s) such as CAS name and number, EC name and number, if known;
— Purity and composition of the chemical (in percentage(s) by weight);
— Physical/chemical properties relevant to the conduct of the study (e.g. physical state, stability, volatility, pH and
water solubility if known);
— Treatment of the test/control chemicals prior to testing, if applicable (e.g. warming, grinding);
— Storage conditions;
Justification of the RhE model and protocol used
Test Conditions:
— Cell system used;
— Complete supporting information for the specific RhE model used including its performance. This should
include, but is not limited to;
i) viability
ii) barrier function
iii) morphology
iv) reproducibility and predictivity
v) Quality controls (QC) of the model
— Details of the test procedure used;
— Test doses used, duration of exposure and post treatment incubation period;
— Description of any modifications of the test procedure;

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— Reference to historical data of the model. This should include, but is not limited to:
i) acceptability of the QC data with reference to historical batch data
ii) acceptability of the positive and negative control values with reference to positive and negative control
means and ranges
— Description of evaluation criteria used including the justification for the selection of the cut-off point(s) for the
prediction model;
— Reference to historical control data;
Results:
— Tabulation of data from individual test chemicals for each run and each replicate measurement;
— Indication of controls used for direct MTT-reducers and/or colouring test chemicals;
— Description of other effects observed;
Discussion of the results
Conclusion
LITERATURE
(1) UN (2009), United Nations Globally Harmonised System of Classification and Labelling of Chemicals (GHS),
Third revised edition, UN New York and Geneva. Available at: [http://www.unece.org/trans/danger/publi/ghs/ghs_
rev03/03files_e.html]
(2) EC-ECVAM (2009), Statement on the “Performance under UN GHS of three in vitro assays for skin irritation
testing and the adaptation of the Reference Chemicals and Defined Accuracy Values of the ECVAM skin irritation
Performance Standards”, issued by the ECVAM Scientific Advisory Committee (ESAC30), 9 April 2009. Available
at: [http://ecvam.jrc.ec.europa.eu]
(3) Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on
classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC
and 1999/45/EC, and amending Regulation (EC) No 1907/2006. OJ L 353, 31.12.2008, p. 1.
(4) OECD (2004), Acute Dermal Irritation/Corrosion, OECD Guideline for the Testing of Chemicals No 404, OECD,
Paris. Available at: [http://www.oecd.org/env/testguidelines]
(5) OECD (2004), In Vitro Skin Corrosion: Transcutaneous Electrical Resistance (TER), OECD Guideline for the
Testing of Chemicals No 430, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]
(6) OECD (2004), In Vitro Skin Corrosion: Human Skin Model Test, OECD Guideline for the Testing of Chemicals
No 431, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]
(7) OECD (2006), In Vitro Membrane Barrier Test Method for Skin Corrosion, OECD Guideline for the Testing of
Chemicals No 435, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]
(8) EC-ECVAM (2009), Performance Standards for in vitro skin irritation test methods based on Reconstructed human
Epidermis (RhE)? Available at: [http://ecvam.jrc.ec.europa.eu]
(9) OECD (2005), Guidance Document on the Validation and International Acceptance of New or Updated Test
Methods for Hazard Assessment, OECD Series on Testing and Assessment No 34, OECD, Paris. Available at:
[http://www.oecd.org/env/testguidelines]
(10) Fentem, J.H., Briggs, D., Chesné, C., Elliot, G.R., Harbell, J.W., Heylings, J.R., Portes, P., Roguet, R., van de Sandt,
J.J. M. and Botham, P. (2001), A prevalidation study on in vitro tests for acute skin irritation, Results and
evaluation by the Management Team, Toxicol. in Vitro 15, 57-93.
(11) Portes, P., Grandidier, M.-H., Cohen, C. and Roguet, R. (2002), Refinement of the EPISKIN protocol for the
assessment of acute skin irritation of chemicals: follow-up to the ECVAM prevalidation study, Toxicol. in Vitro
16, 765-770.
(12) Kandárová, H., Liebsch, M., Genschow, E., Gerner, I., Traue, D., Slawik, B. and Spielmann, H. (2004), Opti
misation of the EpiDerm test protocol for the upcoming ECVAM validation study on in vitro skin irritation tests,
ALTEX 21, 107-114.
(13) Kandárová, H., Liebsch, M., Gerner, I., Schmidt, E., Genschow, E., Traue, D. and Spielmann, H. (2005), The
EpiDerm test protocol for the upcoming ECVAM validation study on in vitro skin irritation tests — An
assessment of the performance of the optimised test, ATLA 33, 351-367.

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(14) Cotovio, J., Grandidier, M.-H., Portes, P., Roguet, R. and Rubinsteen, G. (2005), The in vitro acute skin irritation of
chemicals: optimisation of the EPISKIN prediction model within the framework of the ECVAM validation process,
ATLA 33, 329-349.
(15) Zuang, V., Balls, M., Botham, P.A., Coquette, A., Corsini, E., Curren, R.D., Elliot, G.R., Fentem, J.H., Heylings, J.R.,
Liebsch, M., Medina, J., Roguet, R., van De Sandt, J.J.M., Wiemann, C. and Worth, A. (2002), Follow-up to the
ECVAM prevalidation study on in vitro tests for acute skin irritation, The European Centre for the Validation of
Alternative Methods Skin Irritation Task Force report 2, ATLA 30, 109-129.
(16) Spielmann, H., mailto:Hoffmann, S., Liebsch, M., Botham, P., Fentem, J., Eskes, C., Roguet, R., Cotovio, J., Cole, T.,
Worth, A., Heylings, J., Jones, P., Robles, C., Kandárová, H., mailto:Gamer, A., Remmele, M., Curren, R., Raabe, H.,
Cockshott, A., Gerner, I. and Zuang, V. (2007), The ECVAM international validation study on in vitro tests for
acute skin irritation: Report on the validity of the EPISKIN and EpiDerm assays and on the skin integrity function
test, ATLA 35, 559-601.
(17) Hoffmann, S. (2006), ECVAM skin irritation validation study phase II: Analysis of the primary endpoint MTT and
the secondary endpoint IL1-α. Available at: [http://ecvam.jrc.ec.europa.eu]
(18) Eskes, C., Cole, T., Hoffmann, S., Worth, A., Cockshott, A., Gerner, I. and Zuang, V. (2007), The ECVAM
international validation study on in vitro tests for acute skin irritation: selection of test chemicals, ATLA 35,
603-619.
(19) Cotovio, J., Grandidier, M.-H., Lelièvre, D., Roguet, R., Tinois-Tessonneaud, E. and Leclaire, J. (2007), In vitro acute
skin irritancy of chemicals using the validated EPISKIN model in a tiered strategy — Results and performances
with 184 cosmetic ingredients, AATEX, 14, 351-358.
(20) EC-ECVAM (2007), Statement on the validity of in vitro tests for skin irritation, issued by the ECVAM Scientific
Advisory Committee (ESAC26), 27 April 2007. Available at: [http://ecvam.jrc.ec.europa.eu]
(21) EC-ECVAM (2007), Performance Standards for applying human skin models to in vitro skin irritation testing.
Available at: [http://ecvam.jrc.ec.europa.eu]
(22) EC-ECVAM (2008), Statement on the scientific validity of in vitro tests for skin irritation testing, issued by the
ECVAM Scientific Advisory Committee (ESAC29), 5 November 2008. Available at: [http://ecvam.jrc.ec.europa.eu]
(23) OECD (2010), Explanatory background document to the OECD draft Test Guideline on in vitro skin irritation
testing. OECD Series on Testing and Assessment, No 137, OECD, Paris. Available at: [http://www.oecd.org/
document/24/0,3746,en_2649_34377_47858904_1_1_1_1,00.html]
(24) Welss, T., Basketter, D.A. and Schrder, K.R. (2004), In vitro skin irritation: fact and future. State of the art review
of mechanisms and models, Toxicol. in Vitro 18, 231-243.
(25) Mosmann, T. (1983), Rapid colorimetric assay for cellular growth and survival: application to proliferation and
cytotoxicity assays, J. Immunol. Methods 65, 55-63.
(26) EpiSkin TM SOP, Version 1.8 (February 2009), ECVAM Skin Irritation Validation Study: Validation of the
EpiSkin TM test method 15 min-42 hours for the prediction of acute skin irritation of chemicals. Available at:
[http://ecvam.jrc.ec.europa.eu]
(27) EpiDerm TM SOP, Version 7.0 (Revised March 2009), Protocol for: In vitro EpiDerm TM skin irritation test (EPI-200-
SIT), For use with MatTek Corporation’s reconstructed human epidermal model EpiDerm (EPI-200). Available at:
[http://ecvam.jrc.ec.europa.eu]
(28) SkinEthic TM RHE SOP, Version 2.0 (February 2009), SkinEthic skin irritation test-42a test method for the
prediction of acute skin irritation of chemicals: 42 minutes application + 42 hours post-incubation. Available
at: [http://ecvam.jrc.ec.europa.eu]
(29) Harvell, J.D., Lamminstausta, K., and Maibach, H.I. (1995), Irritant contact dermatitis, In: Practical Contact
Dermatitis, pp 7-18, (Ed. Guin J. D.). Mc Graw-Hill, New York.
(30) Commission Directive 2001/59/EC of 6 August 2001 adapting to technical progress for the 28th time Council
Directive 67/548/EEC on the approximation of laws, regulations and administrative provisions relating to the
classification, packaging and labelling of dangerous substances, OJ L 225, 21.8.2001, p. 1.
(31) Basketter, D.A., York, M., McFadden, J.P. and Robinson, M.K. (2004), Determination of skin irritation potential in
the human 4-h patch test. Contact Dermatitis 51, 1-4.

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(32) Jirova, D., Liebsch, M., Basketter, D., Spiller, E., Kejlova, K., Bendova, H., Marriott, M. and Kandarova, H. (2007),
Comparison of human skin irritation and photo-irritation patch test data with cellular in vitro assays and animal
in vivo data, ALTEX, 14, 359-365.
(33) Jírová, D., Basketter, D., Liebsch, M., Bendová, H., Kejlová, K., Marriott, M. and Kandárová, H. (2010), Comparison
of human skin irritation patch test data with in vitro skin irritation assays and animal data, Contact Dermatitis,
62, 109-116.
Appendix 1
Definitions
Accuracy: The closeness of agreement between test method results and accepted reference values. It is a measure of test
method performance and one aspect of relevance. The term is often used interchangeably with “concordance” to mean
the proportion of correct outcomes of a test method (9).
Cell viability: Parameter measuring total activity of a cell population e.g. as ability of cellular mitochondrial dehy
drogenases to reduce the vital dye MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Thiazolyl blue),
which depending on the endpoint measured and the test design used, correlates with the total number and/or vitality
of living cells.
Concordance: This is a measure of test method performance for test methods that give a categorical result, and is one
aspect of relevance. The term is used interchangeably with accuracy, and is defined as the proportion of all chemicals
tested that are correctly classified as positive or negative. (9).
ET 50 : Can be estimated by determination of the exposure time required to reduce cell viability by 50 % upon
application of the marker ch