Allergic Contact Dermatitis Background

Allergic Contact Dermatitis Background

Allergic contact dermatitis (ACD) is a delayed type of induced sensitivity (allergy) resulting from cutaneous contact with a specific allergen to which the patient has developed a specific sensitivity. This allergic reaction causes inflammation of the skin manifested by varying degrees of erythema, edema, and vesiculation.

The term contact dermatitis sometimes is used incorrectly as a synonym for allergic contact dermatitis. Contact dermatitis is inflammation of the skin induced by chemicals that directly damage the skin (see Irritant Contact Dermatitis) and by specific sensitivity in the case of allergic contact dermatitis.

Jadassohn first described allergic contact dermatitis in 1895. He developed the patch test to identify the chemicals to which the patient was allergic. Sulzberger popularized patch testing in the United States in the 1930s. The Finn chamber method for patch testing was designed in the 1970s; these chambers consist of small metal cups, typically attached to strips of tape, filled with allergens dispersed in either petrolatum or water. The thin-layer rapid use epicutaneous (TRUE) test for patch testing became available in the United States in the 1990s.

The importance of specific substances as causes of allergic contact dermatitis varies with the prevalence of that substance in the environment. Mercury compounds once were significant causes of allergic contact dermatitis but rarely are used as topical medications and, currently, are uncommon as a cause of allergic contact dermatitis. Ethylenediamine, which was present in the original Mycolog cream, declined as a primary cause of allergic contact dermatitis once Mycolog cream was reformulated to no longer contain this allergen.

A detailed history, both before and after patch testing, is crucial in evaluating individuals with allergic contact dermatitis. Before patch testing, the history identifies potential causes of allergic contact dermatitis and the materials to which individuals are exposed that should be included in patch testing. After patch testing, the history determines the clinical significance of the findings. (See Clinical.)

Topical corticosteroids are the mainstay of treatment, while a variety of symptomatic treatments can provide short-term relief of pruritus. However, the definitive treatment of allergic contact dermatitis is the identification and removal of any potential causal agents; otherwise, the patient is at increased risk for chronic or recurrent dermatitis. (See Treatment.)

Go to Irritant Contact Dermatitis, Pediatric Contact Dermatitis, and Protein Contact Dermatitis for complete information on these topics.

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