In vitro measurement of skin sensitization hazard of mixtures and finished products: Results obtained with the SENS-IS assays

Abstract Product safety evaluation in the EU is based on data mainly obtained on individual ingredients. However, mixture effects have been demonstrated in numerous skin sensitization studies due to the presence of irritating chemicals or to modification of dermal absorption. To evaluate the ability of the SENS-IS assay to detect such mixture effects, we performed three sets of experiments: First, the importance of the vehicle on absorption of individual ingredients was evaluated by testing the effect of commonly used cosmetic preparations on the sensitizing potential of 3 chemical allergens and 2 fragrance blends. The sensitizing potential of the 3 allergens was significantly reduced when tested in microemulsion while the “cleansing water” preparation significantly increased it. Water in oil, oil in water or oil preparations had significant but more moderate (enhancing or reducing) effects on the skin sensitization potency of the tested chemicals. We then analyzed the influence of irritants (SDS and Lactic acid) on the sensitizing potency of various allergens. The SENS-IS assay detected an enhancement of the potency of some allergens when mixed with non-irritating concentrations of irritant chemicals. We also tested the influence of mixing different sensitizers to analyze the effect of mixtures on the sensitization threshold. Some mixtures of chemicals, at doses that did not induce a positive signal in the SENS-IS assay alone, became positive, indicating a mixture effect. Finally we tested commercially available finished cosmetic products to find out that they were not all negative. These results indicate that the SENS-IS assay is a valuable source of information when analyzing mixture component effects and finished products.