Kathon CG: cosmetic allergy and patch test sensitization

Three cases of contact allergy to Kathon CG, a preservative for cosmetics and toiletries containing, as active ingredients, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one are presented. In two patients, Kathon CG was contained in a moisturizing cream, and the third was sensitized by a diagnostic patch test. Although it has been used extensively in cosmetics and toiletries for 9 years in Europe and 4 years in the USA, these appear to be the first case reports of non-occupational sensitization to Kathon CG.