[Contact allergies to CN and CS ("tear gas") in participants in demonstrations].

56 occasional demonstrators were interviewed with regard to former skin contact with omega-chloroacetophenone (CN) or ortho-chlorobenzylidene malononitrile (CS). 33 persons (59%) reported skin reactions of various kinds. Patch testing with CN, the structurally related preservative chloroacetamide, and CS revealed clinically relevant reactions to CN in 3 cases and questionable positive reaction to CS in one case. 8 further patients showed mild reactions to CN and CS. We did not find any indication of cross reactions between CN and chloroacetamide.