Allergic contact dermatitis is a skin condition that occurs when your skin comes into contact with allergens, substances to which you are allergic but that are harmless to most people. This condition is not triggered by harsh soaps or acids, for example, because these substances are irritants that will produce a rash on anyone's skin, given enough exposure.
Upon contact with an allergen, the skin reddens and swells and may blister. The blisters may burst, leaving scaly patches. The condition is sometimes difficult to distinguish from other skin conditions, such as atopic eczema (see previous page).
Substances that can trigger allergic contact dermatitis include nickel or nickel-plated items, rubber, hair dyes, and cosmetics such as perfumes and lotions. (Some people are allergic to the chemicals used to preserve cosmetics, while others are allergic to the fragrances used in these products.) Rubber can cause a more serious allergic reaction that goes beyond a simple rash. Some people who are allergic to rubber (including the latex rubber used in rubber gloves) experience itchy, watery eyes and, in some cases, shortness of breath that could lead to anaphylactic shock (see page 383), a potentially fatal allergic reaction. Chromium contained in cement, leather, paints, and antirust products also can produce allergic contact dermatitis. Rashes produced by plants such as poison ivy, poison oak, and poison sumac also are considered allergic contact dermatitis. People who are sensitive to poison ivy, oak, and sumac also may be allergic to the oils contained in mango skins and cashew nut shells.
To diagnose allergic contact dermatitis and to determine its cause, your doctor will examine your rash and ask questions about the materials you use at home and at work. He or she may perform a patch test, in which small amounts of suspected allergens are applied to your skin for a couple of days. If an area of skin becomes inflamed, that substance may be an allergen for you.
The rash produced by allergic contact dermatitis will usually clear up on its own once the allergen has been removed. The only way to prevent the condition from recurring is to avoid all contact with the allergen. A dermatologist can help you identify your allergens.
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