title: Coal tar phototoxicity: characteristics of the smarting reaction.
abstract: We examined the properties and ultraviolet exposure parameters of tar smarts in an effort to elucidate the mechanisms involved. We showed that irradiation with 1 minimal smarting dose (MSD) of UVA immediately following tar removal lowered the MSD for 6 h, demonstrated by subsequent challenge with UVA. Following 3 MSDs this "memory" effect was demonstrable for 24 h. The smarting reaction was area dependent--smaller areas of exposure require higher doses of UVA to induce smarting. Smarting followed reciprocity over a 6-fold range of irradiances (2-12.5 mW/cm2) but higher irradiances required higher doses of UVA, perhaps due to a delay in the recognition and reporting of smarting. The smarting reaction and delayed erythema due to UVA and tar were equally blocked by sunscreen.
mesh_terms: D000328:Adult; D003033:Coal Tar / Q000633:toxicity*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D010787:Photosensitivity Disorders / Q000139:chemically induced* / Q000503:physiopathology; D013473:Sunscreening Agents / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D013473:Sunscreening Agents; D003033:Coal Tar