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EC number: 203-742-5
CAS number: 110-16-7
The Local Lymph Node Assay was performed to
evaluate a possible skin sensitising potential of "Maleic acid"
according to the OECD-Guideline 429, 24 April 2002.
The test substance was used solved in
N,N-Dimethylformamid (DMF)and was administered to three groups of 5
female CBA/Ca mice. Administration was performed epicutaneously to the
dorsal surface of both ears, once a day on three consecutive days. The
volume administered was 25 µL per ear.
A (low dose): 1% (v/v)
solution of "Maleic acid" in DMF
B (mid dose): 2.5%
(v/v) solution of "Maleic acid" in DMF
C (high dose): 5%
(w/v )solution of "Maleic acid" in DMF
Two groups with 5 animals each served as
positive and negative controls. Both control substances were
administered under identical conditions as the test substances.
The following solutions served as control
P (positive control): 25% (v/v) solution
of hexyl cinnamic aldehyde in acetone:olive oil (4:1, v/v)
K (negative control): DMF
5 days after the first topical application,3H-thymidine
was intravenously administered to all mice via a tail vein.
Approximately 5 hours later all animals were sacrificed, the draining
auricular lymph nodes were excised, pooled for each group, and single
cell suspensions were prepared. Then incorporation of3H-methyl
thymidine into the cells was determined (liquid scintillation counter)
and compared with the negative controls. The stimulation index (SI) was
calculated as the ratio of the disintegrations per minute (dpm) of the
dosed groups or of the positive control group to the dpm of the negative
Ear thickness of all animals was measured
before the first and 24 hours after the last administration to get an
information about the skin irritating properties of the substance
All animals survived till the end of the study.
Body mass and body mass gain was in the range
to be expected from animals of the same strain, sex and age.
No skin irritating effects were observed in the
negative control group.
Moderate erythema were noted in all animals of
the positive control group on Days 2-5, in all animals of group C on Day
2, and in few animals of the groups A, B and C on Day 3 indicating local
skin irritation. This irritating effect was confirmed by a statistically
significant difference of the mean ear thickness differences of the
negative control group versus the test substance groups B and C and the
positive control group. There was no statistically significant
difference of the mean ear thickness differences between the negative
control group and the test substance group A.
Different other effects (e.g. lesions, white
crusts) were observed in some animals of the test substance groups
throughout the whole study. The observed lesions were not dose related
and were partially unilateral. They are attributed to scratching because
of a test substance induced itching and not to excessive skin irritation.
incorporation, stimulation indices
The calculated stimulation indices (test
substance/negative control ratio) were decisive for the grading of the
potential of sensitisation: According to the guideline the decision
process with regard to a positive response includes a stimulation index
of equal to or greater than 3, together with consideration of
The SIs of the tested test substance
concentrations were 11.2 (low dose), 22.0 (mid dose) and 31.5 (high
The positive control substance led to a
stimulation index of 14.6, thus demonstrating the validity of the
According to the OECD-Guideline 429, "Skin
Sensitisation: Local Lymph Node Assay", "Maleic acid" is regarded as a sensitiser
in the LLNA.
According to the results of this study and to
the Directive 2001/59/EC for
classification, the test substance "Maleic acid " needs
to be labelled with " R43 May cause sensitisation by skin
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