Rapid increase in contact allergy to Kathon CG in Finland

In unselected eczema patients subjected to routine patch testing, the number with positive reactions to Kathon CG 100 ppm increased from none in 1983 to 0.7% in January-August 1985, and to 4.6% in September 1985 to March 1986. Repeated open application tests (ROAT) with creams containing 7-15 ppm of the isothiazolinones were positive in 12 of 24 patients tested. 2 of the ROAT-positive cases had negative patch tests to 100 ppm Kathon CG, but 1 was positive with 200 ppm. Atopic dermatitis, chronic hand dermatitis and lower leg dermatitis were the most common disorders in the positive patients. The cause of the rapid increase of Kathon CG allergy in Finland during the winter of 1985-1986 was the use of a popular moisturizing cream containing first 19 ppm, then 7 ppm of a mixture of 2 isothiazolinones (Euxyl K 100).