Contact allergy to the preservative Kathon® CG

Abstract

Of 976 patients routinely patch tested with Kathon® CG (Rohm & Haas), 300 ppm. 43 (4.4%) gave a positive reaction. Of 170 patients routinely tested with Kathon® CG 250 ppm, 10 (5.9%) gave a positive reaction. Out of 34 patients tested with serial dilution of Kathon® CG, 17 (50%) reacted to to 100 ppm, 8 to 30 ppm and 2 to 10 ppm. The concentration of 1000 ppm of Rathon® CG was irritant in some cases, but 300 ppm was not irritant. Of the 976 patients tested with Kathon® CG 300 ppm, 8 (0.8%) showed a “flare‐up” reaction, indicating patch test sensitization. Of the 170 tested with Kathon® CG 250 ppm, 2 (1.2%) were sensitized. When the patch‐test‐sensitized patients were retested with serial dilutions, they showed the same pattern as the other patients 13 sensitized patients were use tested and 7 (54%) gave responses. In the literature, Kathon® CG 100 ppm is recommended as the routine patch test concentration. However, 50% of the sensitive persons may then be overlooked. In our clinics. Kathon® CG has become the second most common contact sensitizer, but the sensitivity cannot be traced in all patients with clinically relevant allergy without an unacceptable risk of patch test sensitization. Copyright © 1986, Wiley Blackwell. All rights reserved