Comparative testing for the identification of skin-sensitizing potentials of nonionic sugar lipid surfactants

The Local Lymph Node Assay (LLNA) is the preferred test for the identification of skin-sensitizing potentials of chemicals in Europe and is also the first choice method within REACH. In the formal validation, only a very few surfactant chemicals were evaluated and SDS was identified as a false positive. In this study, 10 nonionic sugar lipid surfactants were tested in an LLNA, guinea pig maximization test (GPMT) and human repeated insult patch test. Of the 10 surfactants tested in the LLNA, 5 showed stimulation indices above 3.0. Three of five positive reactions were concomitant with signs of skin irritation indicated by an increase in ear thickness. In the GPMT, all test products were classified as nonsensitizers. In human volunteers, no skin reactions suggestive of sensitization were reported. In conclusion, these results are indicative of the LLNA overestimating sensitization potentials for this category of chemicals. This may in part be due to irritant effects generated by these surfactants. Until suitable nonanimal alternative tests obtain regulatory acceptance, use of other tests, e.g. GPMTs, may in cases be justified. Results such as these need be taken into account when developing nonanimal alternative methods to ensure reliable data sets for method validation purposes.