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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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Comparable to Guideline.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
see "Principles of method"
according to guideline
OECD Guideline 406 (Skin Sensitisation)
Principles of method if other than guideline:
A modification of the assay by measuring the cell counts instead of radioactive labeling provides comparable sensitivity, and has the advantage that the cell suspension can be further analyzed by different methods (flow cytometry, chemiluminescence responses, immunofluorescence) to gain an insight into mechanistic events. A further modification was done by including the measurement of the ear swelling after treatment leading to a much more simplified and reliable assay (Integrated Model for the Differentiation of Skin reactions (IMDS)). By comparing the specific immune reaction induced by the test item in the draining lymph nodes (LN; cell counts / LN weights) with the immediate unspecific acute skin reaction (ear swelling / ear weight) it is possible to discriminate the irritant potential from the sensitizing potential of the compound tested. International standards have been successfully determined using this modification. Such modifications are also authorized in the Note of Guidance SWP/2145/00 of the CPMP (2001) and OECD guideline 429.
With respect to this simple discrimination between sensitizing and irritant local reactions comparable findings have been reported in the human patch test system.
GLP compliance:
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): o-Dichlorbenzol
- Physical state: clear, colourless liquid
- Analytical purity: 99.9%
- Lot/batch No.: CHH 1470807
- Expiration date of the lot/batch: July 08, 2011
- Storage condition of test material: RT

In vivo test system

Test animals

Details on test animals and environmental conditions:
- Source: Harlan Nederland, Kreuzelweg 53, 5960 AD Horst, Netherland
- Age at study initiation: 8 weeks
- Weight at study initiation: 27¿33 g
- Housing: During the study period the animals were single-housed in Makrolon type II cages.
- Diet: PROVIMI KLIBA SA 3883 maintenance diet, ad libitum
- Water: tap water, ad libitum
- Acclimation period: At least 6 days.

- Temperature (°C): 22±2
- Humidity (%): 40-70
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (LLNA)

acetone/olive oil (4:1 v/v)
0, 2, 10, 50%
No. of animals per dose:
Details on study design:
The test item was applied epicutaneously onto the dorsal part of both ears of the animals. This treatment was repeated on three consecutive days (d1, d2 and d3). The volume administered was 25 µl/ear.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
When it was statistically reasonable, the values from treated groups were compared with those from the control group(s; vehicle) by a one-way analysis of variance (ANOVA) [15, 16] when the variances are considered homogeneous according to a homogeneity testing like Cochran`s test [17]. Alternatively, if the variances are considered to be heterogenous (p¿0.05), a non-parametric Kruskal-Wallis test has been used (Kruskal-Wallis ANOVA) at significance levels of 5%. Two sided multiple test procedures were done according to Dunnett [18, 19] or Bonferroni-Holm [20], respectively. Outlying values in the LN weights were eliminated at a probability level of 99% by Nalimov's method [21]. In addition, for the LLNA/IMDS the smallest significant differences in the means were calculated by Scheffe's method [22], which according to Sachs [17] can be used for both equal and unequal sample sizes.
In this method of statistical processing of measurements a large number of comparisons is made, and as a result of the multiple tests the overall probability of error is considerably greater than the p values suggest (increased number of false-positive results). On the other hand, the known methods of adjusting p values lead to an excessive increase in the number of false negatives. In view of these problems the biological and toxico¬logical relevance is also taken into consideration in the evalua¬tion of statistical significance.

For this reason, in the case of indices only the standard deviations between groups and difference analysis of the mean values were used in the evaluation of the biological relevance.

Results and discussion

In vivo (LLNA)

Remarks on result:
other: See remarks on results.

Any other information on results incl. tables

A LLNA/IMDS was carried out in female NMRI mice after epicutaneous application of a formulation containing 0, 2, 10 or 50% of the test item o-Dichlorbenzol (1,2 -dochlorobenzene) for 3 consecutive days onto both ears of the animals.

The study was conducted according to the modified OECD 429.

A sensitizing potential can be assumed from the increases in cell proliferation in the draining lymph nodes. On the basis of our experiences using this method the positive level had been set to an increase in cell count index by 0.4, which has been exceeded in the high dose group. Differentiation indices (DI) calculated according to our publications which is the quotient of the relative lymph node reaction divided by the relative acute skin reaction were > 1 for the high dose group of the test item, i. e. 2.92. This DI value does also point to a skin sensitizing potential of the test item.

The EC 1.4 value calculated is 32.09% for this test item. In accordance with the classification proposed in the Technical Report No. 78 of the ECETOC this value corresponds to a weak skin sensitizer.

Taken together, a specific activation of the cells of the immune system via dermal route was determined after application of 50% o-Dichlorbenzol by the method used. Thus, o-Dichlorbenzol has to be classified as a weak skin sensitizer.

Applicant's summary and conclusion

Interpretation of results:
Category 1B (indication of skin sensitising potential) based on GHS criteria
According to the weak sensitizing potential, 1,2-dichlorobenzene should be classified and labelled as skin sensitizer.
Executive summary:

The modified Local Lymph Node Assay (IMDS) was performed in 2009 on 24 female NMRI mice of the strain Hsd Win:NMRI (6 animals/test item group and 6 control animals) to determine if there is any specific (sensitizing) or non-specific (irritant) stimulating potential of the test item o-Dichlorbenzol.

The study was conducted according to OECD Guidelines No. 429 and No. 406,

EC Guideline 2004/73/EC (29th Adaptation of Guideline 67/548/EEC, B.42)/Health Effects Test Guideline and OPPTS 870.2600 (EPA) with the following test item concentrations:

0 (vehicle control), 2, 10 and 50%.

The test item was formulated in acetone/olive oil (4:1) (A/OO) to yield a solution.

Compared to vehicle treated animals there were clear increases regarding the weights of the draining lymph nodes and the cell counts in the high dose group. These increases are of statistical significance. The "positive level" of index 1.4 [6, 8, 9] for the cell counts was clearly exceeded at the high dose group.

The 'positive level' of ear swelling, which is 2x10-2 mm increase [8, 9], i.e. about 10% of the control values, has not been reached or exceeded in any dose group.

In conclusion, these results show that the test item o-Dichlorbenzol has at least a weak sensitizing potential in mice after dermal application of a 50% concentration.

Therefore, the concentration of 10% turned out to be the NOEL for the parameters investigated in this study with respect to skin sensitization.