1,2-Benzisothiazolin-3-one (BIT) is an antimicrobial agent that is widely used as a preservative in non-cosmetic products. It has been recognized as an allergen since 1976, and has been shown to be responsible for occupational contact dermatitis in workers involved in the manufacture of paints, plastic emulsions, air fresheners, textile and paper dyes, water softeners, and pottery moulds, and in the metallurgy and carpet industries. We report two cases of allergic contact dermatitis caused by BIT in chemists working on the development of micro-encapsulated perfumes for detergents.