The skin is the largest organ of the body and acts as an interface between the external and internal environments. The skin is a complex organ, and differs in thickness, cornification, pigmentation, occurrence of hair and glands, and blood supply over various regions of the body. The skin is the most common site of work-related toxicity. Skin diseases and chemical burns may account for nearly one-half of all occupational disease. The skin also contains hair follicles, sweat glands, and sebaceous glands. The presence or absence of these appendages varies greatly dependent upon the region of the skin. The skin, particularly the living cells of the epidermis, is an actively metabolizing organ capable of biotransforming many chemical agents. The toxic responses that occur in the skin are dependent not only upon the chemical nature of the agent, but also upon the site of absorption and method of application.