COMMENTARY

Patients With Atopic Dermatitis Exhibit Hypersensitivity Reactions to Allergens

Graeme M. Lipper, MD

Disclosures

September 27, 2013

Cutaneous Delayed-Type Hypersensitivity in Patients With Atopic Dermatitis

Malajian D, Belsito DV
J Am Acad Dermatol. 2013;69:232-237

Study Summary

When confronted with chronic eczematous dermatitis, clinicians should try to differentiate between intrinsic (atopic dermatitis [AD]) and extrinsic (allergic or irritant contact dermatitis) causes. AD is a chronic, recurrent dermatitis associated with asthma and allergic rhinitis, whereas allergic contact dermatitis (ACD) is a T-cell-mediated delayed-type hypersensitivity reaction caused by cutaneous exposure to an exogenous allergen.

Differentiating these conditions is important from both a prognostic and therapeutic standpoint. Children and adults with AD can expect chronic, relapsing dermatitis. In contrast, in persons with isolated ACD, dermatitis typically clears with avoidance of the precipitating allergens.

Differentiating AD from ACD can be challenging in individuals with features of both conditions. Although some studies suggest patients with AD are less likely to develop contact sensitivity to allergens,[1] others show that those with AD have a greater risk of developing ACD.[2]

To address this controversy, Malajian and Belsito did a retrospective review of patch test results from 2305 patients with (n = 297) or without (n = 2008) a history of mild to moderate AD (dermatitis involving up to 25% body surface area). This cohort contained more females than males (1478 vs 825, respectively), and patients underwent patch testing to the North American Contact Dermatitis Group standard allergen series. To avoid false-positive patch test results due to generalized skin hypersensitivity (the "angry back" reaction), patients with flaring dermatitis (> 25% body surface area affected) were excluded.

Intriguingly, Malajian and Belsito found that patients with AD were more likely to have at least 1 positive patch test result (71.72%) than nonatopic controls (64.49%). In addition:

1. Patients with AD had a much higher incidence of positive reactions to nickel sulfate (21.21% vs 11.95%), cobalt chloride (14.14% vs 7.72%), and potassium dichromate (7.07% vs 3.34%) than nonatopic controls.

2. Patients with AD in this cohort did not show a higher incidence of positive reactions to fragrance mix or balsam of Peru.

3. These results were not gender-specific.

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