Polysensitisation in a laboratory scientist associated with allergic contact dermatitis from methylisothiazolinone in skin cleansers.

Polysensitisation refers to reactivity to three or more allergens on epicutaneous patch testing, and is likely to affect a distinct subgroup of individuals with allergic contact dermatitis (ACD). Methylisothiazolinone (MIT) is an increasingly prevalent allergen, recently having been described as occurring in epidemic proportions. We report a patient with ACD to 12 allergens, including MIT, and discuss the implications of polysensitisation and the likely need for repeat patch testing in such patients if they subsequently re-present with dermatitis.