Contact Dermatitis Health Article

Definition

Contact dermatitis is the name for any skin inflammation that occurs when the skin's surface comes in contact with a substance originating outside the body. There are two major categories of contact dermatitis, irritant and allergic. Irritant dermatitis is essentially a direct injury to the skin, caused by such compounds as acids, alkalis, phenol, and detergents. The immune system is not involved in irritant dermatitis, and the person's skin is damaged without prior sensitization.

In allergic dermatitis, however, the patient's skin reacts to a substance to which it has become sensitized. A third type of dermatitis, photo contact dermatitis, is triggered by exposure of the skin to light following the application of certain cosmetics or chemicals. Photo contact dermatitis may be either irritant or allergic.

Description

Contact dermatitis may be either an acute or chronic skin disorder. In general, allergic contact dermatitis is more severe and acute in its onset than irritant contact dermatitis. In irritant contact dermatitis, the rash is usually limited to the area that was exposed to the substance, whereas in allergic contact dermatitis, the rash often spreads beyond the area directly exposed to the allergen. Irritant contact dermatitis most commonly affects the hands, while allergic contact dermatitis may be found on almost any part of the body, including the armpits and genitals. Allergic contact dermatitis is more likely to involve swelling of the skin and the development of small fluid-filled blisters than irritant contact dermatitis.

Photo contact dermatitis is usually limited to the area of skin exposed to direct light. If the substance that was applied to the skin was changed to an irritant by light exposure, the primary symptom is a burning sensation resembling sunburn. If the substance was changed to an allergen, the primary sensation is itching.

Demographics

Contact dermatitis is a common complaint in people of all ages, in part because of the large number of potential irritants and allergens in the contemporary environment. One textbook on contact dermatitis runs to over 1,100 pages of descriptions of the various manufactured products and other substances that can cause these skin reactions.

In the United States, contact dermatitis ranks among the top 10 reasons for visits to primary care doctors and accounts for 7 percent of all visits to dermatologists. Every year between 10 and 50 million Americans in all age groups develop an allergic rash following contact with poison ivy or poison oak.

About 20 percent of children in the general United States population develop allergic contact dermatitis at some point prior to adolescence. Between 20 percent and 35 percent of healthy children react to one or more allergens on standard patch tests. Children of parents with allergic contact dermatitis have a 60 percent greater chance of having a positive reaction on a patch test themselves.

Contact dermatitis is more likely to affect Caucasians than African, Asian, or Native Americans. People with fair skin and red hair are particularly susceptible to contact dermatitis.

With regard to sex, girls are twice as likely as boys to develop both irritant and allergic skin reactions.