A Quantitative Risk Assessment of the Skin Sensitization Induction Potential of the Kathon CG Preservative in Rinse-off and Leave-on Personal Care and Cosmetic Products.

BACKGROUND Kathon CG is a commonly used cosmetic-grade preservative that contains active ingredients methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI). OBJECTIVE The aim of the study was to perform a skin sensitization induction risk assessment of daily exposure to Kathon CG after use of various personal care and cosmetic products. METHODS We calculated an estimated daily consumer exposure level for rinse-off and leave-on products using the amount of product applied per application, number of applications per day, a retention factor, the MCI/MI concentration, and body surface area values. We assumed that the products contained the maximum recommended safe concentration of MCI/MI: 15 ppm in rinse-off products and 7.5 ppm in leave-on products. We compared estimated consumer exposure levels with the no expected sensitization induction level for MCI/MI and applied sensitization assessment factors to calculate product-specific margins of safety (MOSs). CONCLUSIONS The MOSs for rinse-off products ranged from 5 to 63, whereas the MOSs for leave-on products ranged from 0.03 to 1.49. Overall, our results provide evidence that some leave-on products containing the maximum recommended safe concentration of Kathon CG may increase the risk of sensitization induction due to exposure to MCI/MI. In contrast, rinse-off products were not associated with a potential increased risk of skin sensitization induction.