localized redness and swelling of the skin, together with the formation of vesicles (blisters) in more severe cases, caused by skin contact with irritating chemical substances. Certain chemicals, such as lime or nitric acid, produce inflammation in all persons on first contact. Other agents, ordinarily innocuous (e.g., cosmetics, soaps, clothing), cause inflammation after susceptible persons acquire sensitivity by repeated exposure. Prevention of contact dermatitis rests upon the identification of the particular irritant and its subsequent avoidance.