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Clinical features and diagnosis of allergic contact dermatitis

James Yiannias, MD
Section Editor
Joseph Fowler, MD
Deputy Editor
Rosamaria Corona, MD, DSc


Allergic contact dermatitis (ACD) is the classic presentation of a T-cell-mediated, delayed-type hypersensitivity response to exogenous agents [1,2]. The words "dermatitis" and "eczema" are often used interchangeably to describe a pattern of inflammation of the skin characterized acutely by erythema, vesiculation, and pruritus. Chronic exposure typically leads to moderation of the erythema accompanied by lichenification and persistence of itch. The clinical presentation may vary depending upon the triggering agent and individual's reactivity, but, in most cases, the lesions are primarily confined to the site of contact [3,4].

This topic will discuss the clinical presentation, diagnosis, and differential diagnosis of ACD. The pathophysiology, patch testing for, and management of ACD are discussed separately. (See "Basic mechanisms and pathophysiology of allergic contact dermatitis" and "Patch testing" and "Management of allergic contact dermatitis".)


The incidence and prevalence of ACD in the general population are not known. Data are often extrapolated from surveillance studies on occupational dermatitis. In industrialized nations, up to 30 percent of all occupational diseases involve the skin. Irritant and contact dermatitis account for more than 90 percent of cases [5].

Surveillance studies have reported an annual incidence of contact dermatitis (including irritant and ACD) of 13 to 34 cases per 100,000 workers [6-8]. The agents most frequently implicated included latex materials, protective equipment, soap and cleansers, resins, and acrylics. Information on the main allergens responsible for contact dermatitis in the general population is derived from retrospective studies of patch testing referral centers. In one study, metals, fragrances, topical antibiotics, preservatives, chemicals used in hair care products, topical corticosteroids, glues, plastics, and rubber were the most common allergen groups associated with positive patch test reaction [9]. Among children, nickel sulfate, ammonium persulfate, gold sodium thiosulfate, thimerosal, and toluene-2,5-diamine (p-toluenediamine) are the most common sensitizers [10]. (See "Common allergens in allergic contact dermatitis".)

Multiple studies from around the world indicate that, of patients presenting for patch testing, 20 to up to 40 percent will be allergic to nickel [11-16]. In North America, the most common cause of ACD is from contact with poison ivy, oak, and sumac. (See "Poison ivy (Toxicodendron) dermatitis".)

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Literature review current through: Nov 2017. | This topic last updated: Dec 11, 2017.
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