Occupational induction of hypersensitivity after an accidental exposure to chloromethylisothiazolinone and methylisothiazolinone (CMI/MI) in an industrial worker.

A process worker in a paper chemical plant developed an immediate local dermal irritation and delayed bullous dermatitis due to induction of hypersensitivity following an accidental exposure to chloromethylisothiazolinone and methylisothiazolinone (CMI/MI) biocide. Contact allergy to the isothiazolinone mixture was confirmed by skin patch testing. The dermatitis healed in four weeks, and the worker was advised to avoid all CMI/MI containing products. In a one-year follow-up he did not present with any further skin symptoms. Preventive measures are important for avoiding induction of hypersensitivity to concentrated CMI/MI solutions in industrial workers.