Dimethylthiourea, an unexpected hazard for textile workers

Our patient was a 24-year-old female textile cutter who had a conjunctivitis and an erythematous itching dermatitis of the eyelids, nasal mucous membranes, and the corners of the mouth. The patch tests with the standard series and a pharmaceutical test battery were negative. Further epicutaneous testing revealed a strong positive reaction to the textile cutting patterns she handled, which were duplicated by diazo processing. Specifically, the contact dermatitis reaction was caused by dimethylthiourea, an additive in diazo-sensitized paper.