Isothiazoliones Kathon®

Kathon® is a mix of two chemicals, methylchloroisothiazolinone and methylisothiazolinone. Although both are allergenic, methylchloroisothiazolinone is more allergenic than methylisothiazolinone. An epidemic of allergic reactions occurred in Europe when Kathon® was introduced as a preservative in cosmetics in the 1980s. Based on animal studies, those involved with marketing the preservative had misjudged its allergenicity. Despite Kathon® now being used in only very small amounts in cosmetics (0.0003%–0.0015%), it still causes many allergic reactions.

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