Patients sensitive to phenyl salicylate (salol) were patch-tested to several aryl salicylates. The most powerful derivative wasp-nitrophenyl salicylate (compound 5). This can be explained by an unusually good interaction with protein (nucleophilic substitution on the carboxyl carbon). All these results were confirmed by experimental sensitization of guinea pigs to salol and cross-reaction to substituted salols. The results are in line with current theory of allergic contact dermatitis, i.e., an in vivo formation of a hapten-protein conjugate.