Contact allergy caused by isothiazolinone derivatives: an overview of non-cosmetic and unusual cosmetic sources.

The isothiazolinone derivatives, methylchloroisothiazolinone (MCI), methylisothiazolinone (MI), benzisothiazolinone (BIT), and octylisothiazolinone (OIT), owing to their strong bactericide, fungicide and algicide properties, are widely used in non-cosmetic products, such as chemical (industrial) products, household detergents, and water-based paints, and the former two derivatives are also used in cosmetic products. However, given their inherent sensitization potential (with MCI > MI > BIT > OIT), allergic contact dermatitis is frequently observed, both in consumers as well as workers in various industries. In this review, we provide an update on the use of MCI/MI and MI in cosmetics, highlighting certain aspects of MI; the use of excessive concentrations, the presence in some less familiar cosmetic products, and the association with unusual clinical manifestations. Furthermore, the use of isothiazolinones in dish-washing and washing-machine liquids, cleaning agents for dental care, and their general presence in multi-purpose household detergents, which may elicit (airborne) allergic contact dermatitis, is discussed. Finally, we provide a brief overview of the use of isothiazolinone derivatives in the paint and textile industry, and of OIT in the leather industry in particular.