Discordant results were observed when testing five prototype polyfunctional silicone materials for skin sensitization potential in the murine local lymph node assay (LLNA) and in the guinea pig maximization test (GPMT). While all five silicone materials were consistently negative in the GPMT, the testing in the LLNA revealed weak to moderate skin sensitisation potential for four of the five test materials. Neither study quality nor other known chemical factors could explain these findings. Further analysis did not provide sufficient evidence for a link between the LLNA responses and the irritancy of the test substances. Only in the case of one of the test materials, the occurrence of an excessive level of irritation could be linked to the positive LLNA result. Considering all existing information including physico-chemical and structure activity and animal data as well as existing human experience from silicone exposures at the workplace or their use in cosmetic products, the weight of evidence suggests that none of the examined silicone materials represents a significant skin sensitization hazard to humans. The suitability of the LLNA appears questionable for this class of materials. In case of any additional data needs for other or new silicone materials, the skin sensitization testing strategy will require careful evaluation and will need to be set up on a case by case basis.
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