Allergic Contact Dermatitis in Atopic Dermatitis

Abstract

Atopic dermatitis (AD) is a common chronic inflammatory skin disease resulting from a disrupted barrier function and an altered immune mechanism. Sometimes, it is difficult to distinguish between AD, irritant contact dermatitis (ICD), and allergic contact dermatitis (ACD) because they all present as eczematous dermatitis and may co-exist. Impaired barrier function in AD predisposes to the development of both ACD and ICD, as these three conditions share some mechanisms. The prevalence of ACD is at least as common in AD patients as in the general population; therefore, patients with chronic recalcitrant dermatitis should be evaluated for and considered for patch testing. Patch testing should also be undertaken in difficult-to-control or new-onset dermatitis in patients with AD, as avoiding the culprit allergen(s), along with barrier repair and infection control, will lead to improvement of symptoms. There are some special considerations when patch testing in patients with AD. Patch testing should include a standard basic screen in addition to the components of the emollients and cleansers, topical antibiotics, and topical corticosteroids used by the patient. ‘Hypoallergenic’ products without fragrances and strongly allergenic preservatives are commonly recommended in order to minimize the risk of irritation and sensitization via inflamed skin; however, AD patients are often sensitized to weakly potent allergens. Therefore, testing for an extended series of weak allergens used in personal care products and medicaments is critically important. Atopy patch testing (APT) may be also performed as an additional test to detect food and aeroallergen triggers of dermatitis in AD, if clinically indicated. This type of testing is also indicated in patients with a history of perioral eczema and no history of immediate hypersensitivity symptoms to the specific food tested. Aeroallergen APT is specifically indicated in seasonal dermatitis on exposed skin.