Thymol

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

Data is from peer reviewed journal

Data source

Reference

Reference Type:

publication

Title:

The Freund's Complete Adjuvant Test and the Open Epicutaneous Test

Author:

G. Klecak

Year:

1985

Bibliographic source:

Curr. Probl. Derm., vol.14, pp.152-171 (Karger, Basel 1985)

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: as mentioned below

Principles of method if other than guideline:

An Open Epicutaneous Test (OET) was performed on guinea pigs to assess the skin sensitization potential of test chemical Thymol (CAS no: 89-83-8).

GLP compliance:

not specified

Type of study:

open epicutaneous test

Justification for non-LLNA method:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Thymol

EC Number:

201-944-8

EC Name:

Thymol

Cas Number:

89-83-8

Molecular formula:

C10H14O

IUPAC Name:

5-methyl-2-(propan-2-yl)phenol

Details on test material:

- IUPAC Name: Thymol- InChI: 1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3- Smiles: c1(c(cc(C)cc1)O)C(C)C- Molecular formula :C10H14O- Molecular weight :150.2196 g/mol- Substance type:Organic- Physical state:Solid

Specific details on test material used for the study:

- IUPAC Name: Thymol- InChI: 1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3- Smiles: c1(c(cc(C)cc1)O)C(C)C- Molecular formula :C10H14O- Molecular weight :150.2196 g/mol- Substance type:Organic- Physical state:Solid, white crystalline powder, thyme-like, aromatic odor

In vivo test system

Test animals

Species:

guinea pig

Strain:

not specified

Sex:

male/female

Details on test animals and environmental conditions:

- Weight at study initiation: 300-450g

Study design: in vivo (non-LLNA)

Induction

Route:

epicutaneous, open

Vehicle:

other: ethanol, acetone, H20, petroleum, PEG and/or other suitable vehicles

Concentration / amount:

Concentration:3% Amount: 0.1ml

Day(s)/duration:

3 weeks (0-21 days)

Adequacy of induction:

not specified

Challenge

Route:

epicutaneous, open

Vehicle:

other: ethanol, acetone, H20, petroleum, PEG and/or other suitable vehicles

Concentration / amount:

Concentration:3% Amount: 0.025ml

Day(s)/duration:

72 hours

Adequacy of challenge:

not specified

No. of animals per dose:

6-8 guinea pigs

Details on study design:

RANGE FINDING TESTS: The pretest was performed to determine the primary irritating threshold concentration of test substances at various concentrations (100, 30, 10 and 3%). In this test, a single application of 0.025 ml of each test concentration was simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. On the basis of pretest, the concentration selected for sensitization test was 3%.MAIN STUDYA. INDUCTION EXPOSURE- No. of exposures: 21- Exposure period:24 hours- Test groups:6-8 guinea pigs- Control group:3 guinea pigs- Site: an area measuring 8 cm2 on the clipped flank skin of the guinea pigs- Frequency of applications: The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks- Duration: 21 days (3 weeks)- Concentrations:3%Amount: 0.1mlB. CHALLENGE EXPOSURE- No. of exposures: 2- Day(s) of challenge: on days 21 and 35- Exposure period:24 hours- Test groups: 6-8 guinea pigs- Control group: 3 guinea pigs- Site: contralateral flank measuring 2 cm2- Concentrations: Concentration:3%Amount: 0.025ml- Evaluation (hr after challenge): 24,48 and/or 72h.

Challenge controls:

Yes concurrent vehicle.

Results and discussion

In vivo (non-LLNA)

Results

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

3%

No. with + reactions:

0

Total no. in group:

8

Clinical observations:

No known signs of skin sensitization were observed.

Remarks on result:

no indication of skin sensitisation

In vivo (LLNA)

Cellular proliferation data / Observations:

No known signs of skin sensitization were observed.

Any other information on results incl. tables

1 day before starting the induction procedure, the threshold irritating concentration of the test material is estimated on the guinea pigs subsequently used for the experimental group, A single application of 0.025 ml of each test concentration (e.g, 100, 30, 10 and 3%) is simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. The minimal irritating and the maximal nonirritating concentrations are determined by an all-or-none criterion. The minimal irritating concentration is defined as the lowest one causing skin irritation. The maximal nonirritating concentration is defined as the highest one not causing macroscopic skin reactions in any of the animals. The estimation of the threshold concentration (minimal irritating and maximal nonirritating concentration) is essential for the evaluation of the allergenic capacity of the test material.On the basis of this pretest, the concentration selected for sensitization test was 3 %.

Applicant's summary and conclusion

Interpretation of results:

other: Not sensitizing

Conclusions:

The test material Thymol (CAS no: 89-83-8) was considered to be not sensitizing on skin of guinea pigs at concentration of 3% in an Open Epicutaneous Test (OET).

Executive summary:

An Open Epicutaneous Test (OET) was performed on guinea pigs to assess the skin sensitization potential of test chemical Thymol (CAS no: 89-83-8).The pretest was performed to determine the primary irritating threshold concentration of test substances at various concentrations (e.g, 100,30,10 and 3%). In this test, a single application of 0.025 ml of each test concentration was simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. On the basis of pretest, the concentration selected for sensitization test was 3 %.On day 1 during induction, 0.1 ml of the test chemical was applied at concentrations of 3 % in vehicle to an area measuring 8 cm2 on the clipped flank skin of the guinea pigs. The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks, usually on the same skin sites. The application sites were left uncovered and the reactions, if continuous daily applications were performed, can be read 24 h after each application, or at the end of each week. To determine whether or not contact sensitization was induced, all groups of guinea pigs previously treated for 21 days, as well as 10 untreated, or only pretreated with the vehicle, controls are tested on days 21 and 35 on the contralateral flank with the test material. This test was performed by applying with a pipette 0.025 ml of chemical to skin areas measuring 2 cm2. The reactions were read after 24, 48 and/or 72h. It was observed that none of the guinea pigs induced contact sensitization at challenge concentration of 3%.Thus the chemicalThymol (CAS no: 89-83-8) was considered to be not sensitizing on skin of guinea pigs at concentration of 3% in an Open Epicutaneous Test (OET).