Contact allergy to the active ingredients of Kathon® CG

The preservative Kathon1 CG is a commercial preparation, consisting of 2 active ingredients and other components. 28 patients with contact allergy to Kathon CG participated in a study in which patch testing was performed with serial dilutions, and with 5 chromatographically separated fractions. All reacted to fraction IV, and 2 patients also to fraction II. Mass spectrometry and nuclear magnetic resonance spectrometry identified fraction II and IV lo be the active ingredients; 2-melhyl-4-isothia-zolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one.