As part of a program to develop methods for diagnosis of exposure to chemical warfare agents, we developed immunochemical methods for detection of adducts of sulfur mustard to keratin in human skin. Three partial sequences of keratins containing glutamine or asparagine adducted with a 2-hydroxyethylthioethyl group at the omega-amide function were synthesized and used as antigens for raising antibodies. After immunization, monoclonal antibodies were obtained with affinity for keratin isolated from human callus exposed to 50 microM sulfur mustard. These antibodies showed binding to the stratum corneum of human skin exposed to low levels of sulfur mustard, as evidenced by immunofluorescence microscopy. This approach opens the way for development of a detection kit that can be applied directly to the skin. To the best of our knowledge, this is the first example of immunochemical detection of adduct formation of toxic chemicals with skin proteins. A similar approach can be followed for skin exposure to environmental pollutants.