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Toxicological information

Skin sensitisation

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Administrative data

skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-07-08 to 2015-08-12
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 guideline
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
adopted 22 July 2010
according to guideline
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
06 July 2012
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Reference substance name:
Reaction mass of Disodium (sulphonatothio)acetate and sodium chloride
EC Number:
Molecular formula:
Reaction mass of Disodium (sulphonatothio)acetate and sodium chloride
Test material form:
Details on test material:
Purity of Test material:
60.9 % Disodium (sulphonatothio)acetate
20.3 % NaCl
4.3 % Na2S2O3
0.6 % NasSO4
5.0 % H2O
Specific details on test material used for the study:
- Source and lot/batch No. of test material: Sample 14/078 from Mollescal HW, charge 10924344R0
- Expiration date of the lot/batch: April 28, 2019

- Storage condition of test material: Room temperature

In vivo test system

Test animals

Details on test animals and environmental conditions:
- Source: Envigo RMS B.V., Inc., Postbus 6174 5960, AD Horst, The Netherlands
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 9 - 11 weeks
- Weight at study initiation: 19.7 - 21.5 g
- Housing: groupwise (Makrolon Type II (pre-test) / III (main study), with wire mesh top)
- Diet: ad libitum, 2018C Teklad Global 18% protein rodent diet
- Water: ad libitum, tap water
- Acclimation period: at least 5 days
- Indication of any skin lesions: No

- Temperature (°C): 22 ± 2
- Humidity (%): 45-65 %
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (LLNA)

other: ethanol/water (3+7, v/v)
5, 10, 25 %
No. of animals per dose:
Details on study design:
A solubility experiment was performed according to the recommendations given by OECD 429. The highest test item concentration, which could be technically used was a 25 % solution in ethanol/water (3+7, v/v). Vortexing and slight warming to <40 °C were used to formulate the test item. At higher concentrations, an applicable formulation of the test item was not achieved, neither by the use of other vehicles nor by using additional methods to formulate the test item (e.g. vortexing, sonicating, warming to 37 °C).
To determine the highest non-irritant test concentration that at the same time did not induce signs of systemic toxicity, a pre-test was performed in two animals.
Two mice were treated by (epidermal) topical application to the dorsal surface of each ear with test item concentrations of 10 and 25 % once daily each on three consecutive days. Prior to the first application of the test item and before sacrifice the body weight was determined. Clinical signs were recorded at least once daily. Eventual signs of local irritation were documented and a score was used to grade a possible erythema of the ear skin. Furthermore, prior to the first application of the test item (day 1), on day 3 and before sacrifice (day 6) the ear thickness was determined using a micrometer. Additionally, for both animals, the ears were punched after sacrifice (day 6) at the apical area using a biopsy punch (Ø 8 mm corresponding to 0.5 cm²) and were immediately pooled per animal and weighed using an analytical balance. Eventual ear irritation was considered to be excessive if an erythema of the ear skin of a score value ≥3 was observed at any observation time and/or if an increase in ear thickness of ≥25 % was recorded on day 3 or day 6 (for detailed results see Appendix 1).
At the tested concentrations the animals neither showed any signs of local skin irritation nor systemic toxicity. Slight substance residuals were observed on the ears of both animals.
Thus, the test item in the main study was assayed at 5, 10, and 25 %. The highest concentration tested was the highest level that could be achieved whilst avoiding systemic toxicity and excessive local skin irritation as confirmed in the pre-experiment.

Topical application
Each test group of mice was treated by (epidermal) topical application to the dorsal surface of each ear with test item concentrations of 5, 10, and 25 % in ethanol/water (3+7, v/v). The application volume, 25 μL/ear/day, was spread over the entire dorsal surface (Ø 8 mm) of each ear once daily for three consecutive days. A further group of mice (control animals) was treated with an equivalent volume of the relevant vehicle alone (control animals).

Administration of 3H-methyl-thymidine
Five days after the first topical application (day 6) 250 μL of phosphate-buffered saline containing 19.8 μCi of 3H-methyl thymidine (equivalent to 79 μCi/mL 3HTdR) were injected into each test and control mouse via the tail vein.

Determination of incorporated 3HTdR
Approximately five hours after treatment with 3HTdR all mice were euthanized by using CO2, which was, after harvesting of the lymph nodes, followed by cervical dislocation to ensure death.
The draining lymph nodes were rapidly excised and pooled per animal (2 nodes per animal). Single cell suspensions (in phosphate buffered saline) of pooled lymph node cells were prepared by gentle mechanical disaggregation through stainless steel gauze (200 μm mesh size). After washing two times with phosphate buffered saline (approx. 10 mL) the lymph node cells were resuspended in 5 % trichloroacetic acid (approx. 3 mL) and incubated at approximately +4 °C for at least 18 hours for precipitation of macromolecules. The precipitates were then resuspended in 5 % trichloroacetic acid (1 mL) and transferred to scintillation vials with 10 mL of scintillation liquid and thoroughly mixed. The level of 3HTdR incorporation was then measured in a β-scintillation counter. Similarly, background 3HTdR levels were also measured in two 1 mL-aliquots of 5 % trichloroacetic acid. The β-scintillation counter expresses 3HTdR incorporation as the number of radioactive disintegrations per minute.

Determination of Lymph Node Weight and Cell Count
After excision, the lymph nodes were pooled per animal and weighed immediately using an analytical balance. Furthermore, the lymph node cell count was determined for each animal. For this, the volume of the cell suspensions was adjusted to an equal final volume and vortexed. Subsequently, individual cell counts were determined using a cell counter (CASY® DT, Schärfe System). The values obtained were taken down manually.

Determination of Ear Weights
After the lymph nodes had been excised, both ears (left and right) of mice were punched at the apical area using a biopsy punch (Ø 8 mm corresponding to 0.5 cm²). For each animal both punches were immediately weighed (pooled per animal) using an analytical balance.

The test item was placed into an appropriate container on a tared balance and ethanol/water (3+7, v/v) was added. The different test item concentrations were prepared individually. The preparations were made freshly and used within two hours before each dosing occasion. Concentrations were in terms of material as supplied.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
The mean values and standard deviations were calculated in the body weight tables, for the ear weights, the lymph node weights and lymph node cell count, and for the DPM values (group mean DPM ± standard deviation).
A statistical analysis was conducted on the DPM values, the ear weights, the lymph node weights and the lymph node cell count to assess whether the difference was statistically significant between the test item groups and negative control group. For all statistical calculations validated statistical program R Script DecisionTree_2.Rnw was used. Statistical significance was set at the five per cent level (p < 0.05).
The Dean-Dixon-Test and Grubb’s Test were used for identification of possible outliers (performed with validated program R Script Outlier.Rnw). An outlier (DPM value for animal 14) was detected in the Grubb’s, but not in the Dean-Dixon-Test and was therefore not excluded from any calculations.
However, both biological and statistical significance were considered together.

Results and discussion

Positive control results:
The positive control substance induced a statistically significant stimulation compared to the control.

In vivo (LLNA)

Resultsopen allclose all
Key result
Test group / Remarks:
5 %
Key result
Test group / Remarks:
10 %
Key result
Test group / Remarks:
25 %
Cellular proliferation data / Observations:
Radioactive labeling is used to measure proliferations.

The EC3 value could not be calculated, since none of the tested concentrations induced a S.I. greater than the threshold value of 3.

No deaths occurred during the study period. No signs of systemic toxicity or local skin irritation were observed during the study period. The animals of the high dose group showed slight substance residuals within the first hour after application from day 1 until day 3.

The measured lymph node weights and –cell counts of all animals treated were recorded after sacrifice. A statistically significant or biologically relevant increase in lymph node weights or –cell counts was not observed in any of the test item treated groups in comparison to the vehicle control group. For BALB/c mice, a cut-off value for the lymph node cell count index of 1.55 was reported for a positive response. The indices determined for the lymph node cell count did not reach or exceed this threshold.

The measured ear weight of all animals treated was recorded on test day 6 (after necropsy). A biologically relevant or statistically significant increase in ear weights was not observed. Furthermore, the cut-off value (1.1) of the ear weight index for a positive response regarding ear skin irritation reported for BALB/c mice was not reached or exceeded in any of the treated groups.

The body weight of the animals, recorded prior to the first application and prior to treatment with 3HTdR, was within the range commonly recorded for animals of this strain and age. Some animals in the vehicle group and in the group treated with 5 % of test item showed a very minor decrease in body weight over the course of the study, which was biologically not relevant.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met