IgE-mediated hypersensitivity and contact sensitivity to multiple environmental allergens in atopic dermatitis

Atopic dermatitis (AD) is a chronic eczematous skin disease that develops in a patient with atopic diathesis, which is characterized by an increased liability to produce IgE antibodies for environmental allergens mostly derived from other living organisms. Experimentally, eczematous skin lesions cannot be induced by immediate IgE-mediated reactions alone. They are produced by cell-mediated allergic contact reactions, and recently contact sensitivity to various environmental allergens has been demonstrated in patients with AD. However, the pathologic role of IgE-mediated skin hypersensitivity or that of delayed-type hypersensitivity to various environmental allergens in AD is not fully evaluated. They have been studied separately and against only specific allergens. Thus, we performed a combined testing procedure consisting of radioallergosorbent test, prick, and scarification patch tests for eight environmental allergens in 97 Japanese adult patients with AD; 48 of them had a history of atopic respiratory diseases (ARD), whereas the remaining 49 had no history of ARD (pure AD).

Patients with AD, particularly those with ARD (AD+ARD), showed a higher incidence of positive radioallergosorbent test and prick test results as well as patch test results against multiple environmental allergens than healthy age-matched control subjects. Among them, we found a significantly high positive correlation between radioallergosorbent test scores and patch test reactions to two allergens, Japanese cedar, and Dermatophagoides farinae allergens in patients with AD. However, the patients with AD displayed a significantly lower incidence of positive patch test reactions to Candida albicans allergen than the healthy control subjects. Patients with AD with negative C albicans patch tests tended to have higher levels of total serum IgE including anti-C albicans IgE antibody. We found negative correlations between total serum IgE levels including specific antibodies and patch test reactions to C albicans allergen.

Except for the dissociated reactivities to C albicans allergen consisting of decreased contact sensitivity and heightened IgE response, generally both IgE-mediated skin hypersensitivity and delayed-type hypersensitivity to various environmental allergens are pronounced in patients with AD. The combined use of these in vivo and in vitro tests is useful to estimate the immunological state of patients with AD.