Contact allergy to isothiazolinone derivatives: unusual clinical presentations.

Contact allergic reactions to the mixture of 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazoline-3-one are most frequently associated with intolerance to cosmetics. The present article points out that such reactions, particularly on the face, can have unusual clinical presentations that are very similar to seborrheic eczema, lupus erythematosus, lymphocytic infiltrate or photodermatitis. Atopic dermatitis is also often erroneously suspected.