Triclosan

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Triclosan was tested for its skin sensitisation potential in a modified Buehler test on Guinea pigs (Product Safety Labs 2635). Triclosan was applied to 10 test animals and DNCB served for positive control.

Prior to testing for sensitisation, a pre-test was conducted for determination of the primary irritation of the test itemal. For this purpose, the fur was removed by clipping the dorsal area and flanks of each test animal. This area was divided into 4 test sites and the test substance was diluted with propylene glycol (PG) to yield concentrations of 95%, 75%, 50%, 25%, 10%, 7%, 5%, 2% and 1%. Each concentration was applied to a test site under occlusive conditions. After 6 hrs of exposure, the dressings were removed. Twenty-four hours after application, each site was evaluated for local skin reactions (erythema). The highest concentration that produced responses in 4 guinea pigs no more severe than 2 scores of 0.5 and 2 scores of zero was established and used for challenge in the main test; based on the findings of the pre-test, the selected concentration for challenge was 5% of test item solution in PG.

For the main test, the fur of the test animals was removed by clipping the dorsal area and flanks one day before testing. For induction 25% test item in PG was initially selected; however, due to the severity of irritation after the 2^nd and 4^th application, the induction concentration was reduced to 10% for inductions 3 and 4, and further decreased to 2% for inductions 5 through 9.

Triclosan was applied onto the skin of each test animal 3 times each week for a 3 week induction period (total of 9 applications). The application site was maintained under occlusive conditions for an exposure period of 6 hours; after removal of the dressing, the application sites were gently cleaned.12 days after last induction, a challenge dose of 5% triclosan in PG was applied to a naive site on each guinea pig, similarly as described above. The sites were evaluated for a sensitization response (erythema) at 24 and 48 hours after challenge. In fact, the application sites were examined for skin reactions, and the findings were scored according to following system: 0 = no reaction, 0.5 = very faint erythema, usually non-confluent, 1 = faint erythema usually confluent, 2 = moderate erythema, 3 = severe erythema with or without edema. In order to evaluate the sensitization response, 2 indices were used; one for incidence and one for severity for both test and positive control animals:

(1)- The incidence index was calculated to evaluate the incidence of erythema (sensitization response) 24 and 48 hours after challenge according to the following formula: lncidence Index = Number of erythema scores> 0.5/Number of animals evaluated.

(2)- The severity index (sensitization produced) at 24 and 48 hours after challenge was calculated using the following formula: Severity Index = Sum of erythema scores /Number of animals evaluated.

The following criteria were used to classify the test substance as a potential contact sensitizer:

(1)- At the 24 and/or48 hour scoring interval, 20% or more (i.e. incidence index of 0.2 or more) of the test animals exhibit a positive response (scores > 0.5) in the absence of similar results in the naive control group.

(2)- The positive reaction must persist to 48 hours in at least one test animal.

Following challenge, triclosan treatment induced weak, non-confluent reactions of very weak erythema (scores of 0.5) in 6/10 animals (not considered to indicate sensitisation). Negative controls showed similar faint erythema reactions in 2/5 animals (scores of 0.5). Positive controls showed strong reactions (scores of 1 to 3) in 10/10 animals. Thus, triclosan was not considered to be sensitizing the the modified Buehler test. This finding was supported by the results of the Maurer optimization test (Maurer 1979) and theadjuvant test with guinea pig (Lachapelle 1979). Thus, based on the negative outcome of these tests, triclosan is not a a skin sensitizer.

Migrated from Short description of key information:
Valid data on the sensitizing potential of triclosan are available. The following studies/publications were retained as key and supporting data for assessment of sensitization.
Triclosan was tested for its skin sensitisation potential in a modified Buehler test on Guinea pigs (key study, Product Safety Labs 2635); the test was conducted according to the US FIFRA §81-6 guideline, which was similar to the OECD TG 406.
As supporting data, a Maurer optimisation test with guinea pig (Maurer 1979) and a Split Adjuvant Test with guinea pig (Lachapelle 1979) based on the technique of Maguire (Estimation of the allergenicity of prospective human contact sensitizers in the guinea pig. pp 67-75 in Animal models in dermatology. Ed. by H.I. Maibach, Churchill Livingstone, Edinburgh 1975) are further available.
Triclosan tested in the Buehler Test was not a contact sensitizer as the substance did not fulfil the criteria for classification as a skin sensitizer (>= 15% of sensitized animals). The positive response to 0.03% DNCB (positive control substance) in acetone validated the test system used in this study. In the Mauer optimisation test, the incidence of positive reactions was similar for triclosan-treated (4/20 after first challenge, 3/20 after second challenge) and negative control animals (4/19 after first challenge, 1/19 after second challenge); thus, triclosan was not a contact a sensitizer in this test. Triclosan evaluated for sensitisation in the Split adjuvant test showed one positive reaction, in one of twenty animals.

Respiratory sensitisation

Endpoint conclusion

Additional information:

Migrated from Short description of key information:
No data available on respiratory sensitisation

Justification for classification or non-classification

Since the results of sensitisation tests with guinea pigs provided no evidence of sensitisation by triclosan following induction exposures of up to 10% (various formulations), triclosan is not a sensitizer in animals.

Thus, triclosan has not to be classified as a skin sensitizer, neither according to the EU Directive 67/548/EEC, nor according to the Annex VI of the CLP regulation.