A detailed history, both before and after patch testing, is crucial in evaluating individuals with allergic contact dermatitis. Potential causes of allergic contact dermatitis and the materials to which individuals are exposed should be included in patch testing. Evaluation of allergic contact dermatitis requires a much more detailed history than most other dermatologic disorders.
Women with lichen sclerosus et atrophicus frequently develop allergic contact dermatitis, complicating the severe chronic vulvar dermatosis. Patch-testing these patients may provide important information that can help in the management of recalcitrant and difficult-to-manage dermatoses.
Patients with a history of atopic dermatitis are at increased risk for nonspecific hand dermatitis and irritant contact dermatitis. They are at lower risk for allergic contact dermatitis to poison ivy.
Individuals with allergic contact dermatitis typically develop dermatitis, within a few days of exposure, in areas that were exposed directly to the allergen. Certain allergens (eg, neomycin) penetrate intact skin poorly, and the onset of dermatitis may be delayed up to 1 week after exposure. A minimum of 10 days is required for individuals to develop specific sensitivity to a new contactant. The immediate onset of dermatitis after initial exposure to material suggests either a cross-sensitization reaction, prior forgotten exposure to the substance, or nonspecific irritant contact dermatitis provoked by the agent in question.
Immediate reactions (ie, visible lesions developing < 30 minutes after exposure) indicate contact urticaria and not allergic contact dermatitis. This is particularly true if the lesions are urticarial in appearance and if the skin reaction is associated with other symptoms, such as distant urticaria, wheezing, periorbital edema, rhinorrhea, or anaphylaxis.
Read more on the presentation of allergic contact dermatitis.
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Cite this: William James. Fast Five Quiz: Dermatitis - Medscape - Nov 04, 2020.