Allergic contact dermatitis.
Once sensitized, epidermal antigen-presenting cells (APCs) called Langerhans cells process the allergen and present it in a complex on the surface of the cell to a CD4+ T cell. Subsequently, inflammatory cytokines and mediators are released, resulting in an allergic cutaneous (eczematous) reaction. Lesions may appear to be vesicular or bullous. Occasionally, a generalized eruption may occur. With repeated exposure, reactions may be acute or chronic.
Common causes of allergic contact dermatitis include toxicodendron plants (poison ivy, oak, and sumac; cashew nut tree; and mango), metals (nickel and gold), topical antibiotics (neomycin and bacitracin), fragrance and Balsam of Peru, deodorant, preservatives (formaldehyde), and rubber (elastic and gloves).
Patch testing is the standard means of detecting which allergen is causing the sensitization in an individual. The Thin-Layer Rapid Use Epicutaneous (TRUE) test or individually prepared aluminum (Finn) chambers containing the most common allergens are applied to the patient's upper back. The patches are removed after 48 hours and read, and then reevaluated at day 4 or 5. Positive reactions appear as eczematous or vesicular papules or plaques.
Treatment includes avoidance of the allergens. Topical corticosteroid creams are helpful. For severe or generalized reactions, oral prednisone may be used. It is important to note that patient may be allergic to topical steroids. Patch testing can be performed to elucidate such allergens.
In contrast, 80% of contact dermatitis reactions are irritant, not allergic. Irritant contact dermatitis results in a local inflammatory reaction in people who have come into contact with a substance. Previous sensitization is not required. The reaction usually occurs immediately after exposure. Common causes include alkalis (detergents, soaps), acids (often found as an industrial work exposure), metals, solvents (occupational dermatitis), hydrocarbons, and chlorinated compounds.
This case and photos were submitted by Dr. Bilu Martin.
BY DONNA BILU MARTIN, MD
Dr. Bilu Martin is a board-certified dermatologist in private practice at Premier Dermatology, MD, in Aventura, Fla. To submit a case for possible publication, send an email to firstname.lastname@example.org.
A 30-YEAR-OLD FEMALE presented with 2 days of intensely pruritic erythematous papules and vesicles on her arms and hands bilaterally. The lesions began appearing 1 day after a camping trip. Her neck, chest, and upper back were clear.
Make the Diagnosis
b) Allergic contact dermatitis
c) Irritant contact dermatitis
d) Polymorphous light eruption
Caption: Courtesy Dr. Donna Bilu Martin
Caption: Photos Courtesy Dr. Donna Bilu Martin
Please Note: Illustration(s) are not available due to copyright restrictions.
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|Title Annotation:||Make the Diagnosis|
|Author:||Martin, Donna Bilu|
|Publication:||Family Practice News|
|Date:||Oct 1, 2018|
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