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Skin sensitisation

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skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
November 2014 - february 2015
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guidelineopen allclose all
according to
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
adopted 22 July 2010
according to
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
GLP compliance:
Type of study:
mouse local lymph node assay (LLNA)

Test material

Test material form:
Details on test material:
- Substance Type: Natural Complex Substance
- CAS-No. 89997-74-0
- EINECS No. 289-711-7
- Description: Dark brown to brown-orange solid
- Batch No. 09/2014
- Purpose of testing: REACH
- Manufactured Date: September 2014
- Expiry Date: 1 September 2016
Specific details on test material used for the study:
dark brown solid block

In vivo test system

Test animals

Details on test animals and environmental conditions:
- Source: Harlan Laboratories Uk, Oxon, UK
- Age at study initiation: 8-12 weeks
- Weight at study initiation: 15-23 g
- Housing: Animals were housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes.
- Diet: Food (2014C Teklad Global Rodent diet supplied by Harlan Laboratories UK Ltd., Oxon, UK), ad libitum
- Water: Mains tap water, ad libitum
- Acclimation period: 5 days

- Temperature: 19-25 °C
- Humidity: 30-70 %
- Air changes: Approximately 15 changes/h
- Photoperiod: 12 h dark / 12 h light

Study design: in vivo (LLNA)

Preliminary screening test:50%, 25% and 10% w/w in DMF
Main test: 10%, 5% and 2.5%w/w in DMF
No. of animals per dose:
Preliminary screening test: One animal/dose
Main test: 5 animals/dose
Details on study design:
- Using available information regarding the irritancy potential of the test item, a preliminary screening test was performed using three mice, one mouse per test item concentration. The mice were treated by daily application of 25 μL of the test item at concentrations of 50%, 25% and 10% w/w in dimethyl formamide, to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The mice were observed twice daily on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Local skin irritation was scored daily. Any clinical signs of toxicity, if present, were also recorded. The body weight was recorded on Day 1 (prior to dosing) and on Day 6.
- The thickness of each ear was measured using a Mitutoyo 547-300S gauge (Mitutoyo Corporation), pre-dose on Day 1, post dose on Day 3 and on Day 6. Any changes in the ear thickness were noted. Mean ear thickness changes were calculated between time periods Days 1 and 3 and Days 1 and 6. A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitization.

- Irritation: No signs of systemic toxicity were noted. Very slight erythema on both ears was noted in the animal treated with the test item at a concentration of 50% w/w in dimethyl formamide. Colorless, sticky residual test item on the ears and fur loss were noted in the animals treated with the test item at concentrations of 50% or 25% w/w in dimethyl formamide.(DMF). A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitization. Based on this information the dose levels selected for the main test were 10%, 5% and 2.5% w/w in DMF.

- Name of test method: Local Lymph Node Assay
- Criteria used to consider a positive response: The test item will be regarded as a sensitizer if at least one concentration of the test item results in a threefold or greater increase in 3HTdR incorporation compared to control values. Any test item failing to produce a threefold or greater increase in 3HTdR incorporation will be classified as a "non sensitizer."

The test item was formulated within two hours of being applied to the test system. It is assumed that the formulation was stable for this duration.
25 µL of control or test material was applied topically on the dorsal surface of both ears using a micropipette daily for three consecutive days (Days 1-3). Five days following the first topical application of the test item or vehicle (Day 6) all mice were injected via the tail vein with 250 μL of phosphate buffered saline (PBS) containing 3H-methyl thymidine (3HTdR: 80 μCi/mL, specific activity 2.0 Ci/mmoL, ARC UK Ltd) giving a total of 20 μCi to each mouse. Five hours later animals were killed by carbon dioxide asphyxiation followed by cervical separation. The lymph nodes from each group were pooled and a single cell suspension was prepared. Cells were washed with phosphate buffered saline (PBS) and precipitated with 5% trichloroacetic acid (TCA) for 18 h at ca. 4 °C. The pellets were recovered by centrifugation and resuspended in 1 mL of TCA and transferred to a vial containing scintillation fluid. 3HTdR incorporation was measured by β-scintillation counting. The "Poly Q™" vials containing the samples and scintillation fluid were placed in the sample changer of the scintillator and left to stand in darkness for approximately 20 minutes. The purpose of this period of time in darkness was to reduce the risk of luminescence, which has been shown to affect the reliability of the results. After approximately twenty minutes, the vials were shaken vigorously. The number of radioactive disintegrations per minute was then measured using the Beckman LS6500 scintillation system (Beckman Instruments Inc, Fullerton, CA, USA).
The proliferation response of lymph node cells was expressed as the number of radioactive disintegrations per minute per animal and as the ratio of 3HTdR incorporation into lymph node cells of test nodes relative to that recorded for the control nodes (Stimulation Index).
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Data was processed to give group mean values for disintegrations per minute and standard deviations where appropriate. Individual and group mean disintegrations per minute values were assessed for dose response relationships. Data was first assessed for suitability by analysis of normality and homogeneity of variance. If the assumptions that the data are both normally distributed and has homogeneity of variances, then parametric one way analysis of variance (ANOVA) and Dunnett’s multiple comparison procedure were used to determine statistical significance. If the assumptions were not met, non-parametric Kruskal-Wallis Rank Sum and Mann-Whitney U test procedures were used.
Probability values (p) were presented as follows:
P<0.001 ***
P<0.01 **
P<0.05 *
P≥0.05 (not significant)

Results and discussion

Positive control results:
The reduced LLNA (rLLNA) , Positive control from study: 41403325 (08 October 2014 to 14 October 2014 ). Positive control: α Hexylcinnamaldehyde, tech., 85% in dimethyl formamide at a concentration of 15% v/v. SI- 5.34

In vivo (LLNA)

Resultsopen allclose all
Test group / Remarks:
test concentration 2.5%
Test group / Remarks:
concentration 5%
Key result
Test group / Remarks:
at 10% concentration

Any other information on results incl. tables

Clinical Observations and Mortality Data

There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.



Body weight change of the test animals between Day 1 and Day 6 were comparable to that observed in the corresponding control group animals over the same period.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
The test item was considered to be a non skin-sensitizer under the conditions of the test.
Executive summary:

A study was performed to assess the skin sensitisation potential of test material in the CBA/Ca strain mouse following topical application to the dorsal surface of the ear. The method was conducted according to the OECD test guideline No 429 and in compliance with GLP.

Following a preliminary screening test in which no clinical signs of toxicity were noted at a concentration of 10% w/w, this concentration was selected as the highest dose investigated in the main test of the Local Lymph Node Assay. Three groups, each of five animals, were treated with 50 µL (25 µL per ear) of the test item as a solution in dimethyl formamide at concentrations of 10%, 5% or 2.5% w/w. A further group of five animals was treated with dimethyl formamide alone.

The Stimulation Index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows:


Concentration (%w/w) in
dimethyl formamide

Stimulation Index













The historical positive control, α-Hexylcinnamaldehyde, gave a SI of 5.34, when tested at 15 % v/v. The test system was therefore considered to be valid.


There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.Body weight change of the test animals between Day 1 and Day 6 were comparable to that observed in the corresponding control group animals over the same period.


Under the test conditions, test material is not classified as a skin sensitiser according to the annex VI of the Regulation EC No. 1272/2008 (CLP) .

This study is considered as acceptable and satisfies the requirement for sensitisation endpoint.