Sensitization to Kathon CG in Geneva and Switzerland.

Between October 1986 and June 1987 we patch tested 420 patients with Kathon CG at 100 ppm and obtained 23 positive reactions (5.5%). The other 5 Swiss university clinics joined our study between January and June 1987 and obtained sensitization rates ranging from 0.7 to 7.5%. The total mean value including Geneva was 3.6%. We did threshold patch testing in 12 patients with the following Kathon CG dilutions: 100, 50, 25, 15 and 7 ppm. We observed progressively diminishing skin reactions, especially below 25 ppm, but we still obtained slight positive reactions in 2 patients with Kathon CG at 7 ppm. Those reactions were relevant because the dermatitis disappeared when the use of Kathon-containing creams was discontinued.