4,6-bis(octylthiomethyl)-o-cresol

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

(adopted in 1981)

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

A valid guinea pig maximization study is available, an additional LLNA is not necessary

Test material

Test material information

Constituent 1

Reference substance name:

4,6-bis(octylthiomethyl)-o-cresol

EC Number:

402-860-6

EC Name:

4,6-bis(octylthiomethyl)-o-cresol

Cas Number:

110553-27-0

Molecular formula:

C25 H44 O S2

IUPAC Name:

2-methyl-4,6-bis[(octylsulfanyl)methyl]phenol

Details on test material:

- Physical state: viscous liquid
- Apperance: yellow, clear
- Storage: at minimum of 19 °C

In vivo test system

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Iffa Credo (Les Oncins - 69210 L'Arbresle - France), Bantin and Kingman (Aldbrough Hull - HU 11 1QE - Great Britain), David Hall (Burton on Trent - DE 13 8RJ - Great Britain), Shamrock Bloservcles (12, route de Saint Come - 7895C Garabals - France)
- Age at study initiation: no data
- Weight at study initiation: 330-500 g
- Housing: in groups of 5 (or of 2 for the preliminary studies) in polystyrene cages
- Diet: ad libitum; Guinea-pig complete pelleted maintenance food (Extra Labo formule "C.15.50" - Ets. Pletrement, Sainte Colorabe - 77650 Longueville, France).
- Water: ad libitum; softened and filtered drinking water (15 µl) (automatic watering system). Bacteriological and chemical controls were performed every six months
- Acclimation period: at least 5 days
- Rationale for choice: the guinea-pig is the most sensitive species for the evaluation of the allergenic potential. Historically, this species is often used a lot for this type of studies and is the species of choice of the various regulatory authorities.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 3
- Humidity (%): 30 -70
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (non-LLNA)

Induction

Induction 1

Route:

intradermal

Vehicle:

other: Vaseline Codex: lot 653 (Laboratoires Aguettant - 1 avenue Carteret, Lyon - France)

Concentration / amount:

100%

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Induction 2

Route:

epicutaneous, occlusive

Vehicle:

other: Vaseline Codex: lot 653 (Laboratoires Aguettant - 1 avenue Carteret, Lyon - France)

Concentration / amount:

100%

Day(s)/duration:

48 hours

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

Challenge

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: Vaseline Codex: lot 653 (Laboratoires Aguettant - 1 avenue Carteret, Lyon - France)

Concentration / amount:

100%

Day(s)/duration:

24 hours

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

Preliminary test: total of 12 animals (2 males + 2 females)/intradermal induction, topical induction and challenge
Test group : 10 males + 10 females. An additional 1 male and 1 female were treated as satellites to allow for possible non treatment-related mortality
Control group: 10 males and 10 females

Details on study design:

RANGE FINDING TESTS
Intradermal Injection
- Number of animals: 2 male + 2 females
- Concentrations: 10 and 50% in Vaseline codex or 100%
- Methodology: same as in main study

Epicutaneous induction exposure:
- Number of animals: 2 male + 2 females
- Concentrations: 50% in Vaseline codex and 100%
- Methodology: same as in main study
- Evaluation (hr after removal of patch): 1 hour

Challenge
- Site/area: Back/ 8 cm2
- Number of animals: 2 male + 2 females
- Concentrations: 50% in Vaseline codex and 100%
- Method: same as in main study
- Evaluation (hr after removal of patch): 24 and 48

MAIN STUDY
A. INDUCTION EXPOSURE
Intradermal Injection
- Site/Area: Back (scapular region)/2 x 4 cm
- No. of injections/animal: 6 injections in pairs each.
- Test substance group: Freund's complete adjuvant blended (1:1, v/v) in 0.9 % NaCl
- Test substance group: undiluted test article
- Test substance group: Freund's complete adjuvant blended (1:1, v/v) in 0.9 % NaCl + undiluted test article
- Control group : Freund's complete adjuvant blended (1:1, v/v) with 0.9 % NaCl
- Control group: Vehicle.
- Control group : Freund's complete adjuvant blended (1:1, v/v) with 0.9 % NaCl + vehicle
- Volume per injection: 0.1 ml/animal
- Evaluation (hr after injection): 24 and 48

Epicutaneous induction exposure:
- Time schedule: 8 days after intradermal induction
- Site: same as intradermal injections (site was pretreated 24 hours before with 0.5 ml per site of 10% w/w sodium lauryl sulphate in Vaseline codex paraffin)
- Area of application: 2 x 4 cm
- Concentrations: undiluted test article (test group), and vehicle (control group)
- Volume applied: 0.5ml/animal
- Type of coverage: occlusive (a 3 x 5 cm waterproof and hypoallergenic adhesive plaster (Blenderm: 3M, Laboratoire des Professions Hedlcales - 10, rue Gabriel Crle - 92210 Malakoff - France). Reinforcement was performed with 4 cm wide linen adhesive tapes applied on hydrophilic gauze
- Duration: 48 hours
- Evaluation (hr after challenge): directly after removal of patch

B. CHALLENGE EXPOSURE (identical treatment for treated and control animals)
- Time schedule: 11 days after end of topical induction
- Site: left flank (test article) and right flank (vehicle)
- Area of application: 2 x 2 cm
- Concentrations: undiluted
- Volume applied: 0.5 ml/animal
- Type of coverage: occlusive (hypoallergenic adhesive plaster (H-IFT - Urgo : Laboratoire de Pansements et d'Hygiene - 42, rue de Longvic - 21300 Chenove - France). Reinforcement was performed with 4 cm wide linen adhesive tapes applied on hydrophilic gauze
- Duration: 24 hours
- Evaluation (hr after challenge): 24 and 48 hours after termination of exposure. Histopathological examination of the skin was performed for all the animals which showed doubtful reactions after macroscopical examination at 24 and 48 hours.

Positive control substance(s):

yes

Remarks:

The sensitivity of the test was evaluated in the test laboratory with known sensitizers as well as known non sensitizers (Dihydrocoumarin, Paraphenylenediamine, Formalin, Penicillin G, Benzocaine, Propylene Glycol).

Results and discussion

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

19

Results 2

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

19

Results 3

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

2

Total no. in group:

20

Results 4

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

2

Total no. in group:

20

Any other information on results incl. tables

PRELIMINARY TEST

Intradermal induction:

At the 24 hour observation time point, the intradermal injection of the undiluted test article (erythema score = 2 (2/4 animals); erythema score = 1 (2/4 animals)) as well as 50% in vaseline (erythema score = 1 (3/4 animals); erythema score = 2 (1/4 animals) caused slight to moderate skin irritations in 4 guinea pigs. At the 48 hour observation point, the intradermal injection of the undiluted test article (erythema score = 2 (4/4 animals) as well as 50% in vaseline (erythema score = 1 (4/4 animals)) caused slight to moderate skin irritations in 4 guinea pigs. A slight skin irritation (erythema score = 1) was seen in only 1/4 guinea pigs at the 24 hour observation time with 10% of the test article in vaseline.

Topical induction:

Only one out of 4 treated animals had a slight erythema after treatment with the undiluted test article (erythema score = 1) or with 50% test article in vaseline (erythema score = 1).

Challenge

No skin irritation was recorded in all 4 animals. On the basis of these results, the undiluted test substance was applied in the main study.

MAIN STUDY

In the control animals, slight desquamation was seen in 4/19 surviving animals at the 48 hour examination following challenge exposures. One female guinea pig died. There was slight desquamation at the site application in the dead control animal. In the treatment group, slight desquamation was evident in 8/20 animals at the 48 hour examination. At the 24 hour examination, no desquamation was seen in any animals, however, 5/20 guinea pigs had an erythema score of 1. At the 48 hour examination, 5 additional guinea pigs had an erythema score of 1. Histopathological biopsies of the cutaneous tissues confirmed a positive skin irritation only in 2 of the10 questionable cases making a total of 2/20 animals (5%) positive for "delayed hypersensitivity". Two cases of mortality were recorded in the treatment group. These animals were replaced with the satellite animals which had undergone simultaneous identical treatment.

POSITIVE CONTROL

The sensitivity of this method was evaluated in the test laboratory using various substances known for their sensitizing potential (or their innocuity). The results obtained are presented in the following table:

Table 1: List of substances tested in the laboratory

Test substance	Results with Histology (% of sensitized animals)
Dihydrocoumarin	100
Paraphenylenediamine	55
Formalin	70
Penicillin G	70
Benzocaine	45
Propylene Glycol	0

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met