[Allergy and atopic eczema: on the value of the "atopy patch test"]

The role of allergic reactions in eliciting and maintaining atopic eczema (AE) is still controversial. In a subgroup of patients with atopic eczema, exacerbations of itching and eczematous skin lesions have been described after contract with aeroallergens. To investigate this observation, an epicutaneous patch test with IgE-inducing allergens (atopy patch test, APT) has been proposed, which results in eczematous skin reactions in 30-70% of AE patients. Usage of allergen concentrations exceeding 5000 PNU/g in petrolatum allows testing on clinically uninvolved skin without potentially irritating epidermal tape stripping. The clinical relevance of positive APT reactions is suggested by comparison of APT with skin prick test, specific IgE, patient's history and eczema pattern. Patients with an eczema pattern with preferred localization of skin lesions in air-exposed areas, a predictive history and raised specific IgE (depending on allergen) were shown to have the highest rate of positive APT. Future controlled studies with allergen avoidance and reexposition may focus on this patient group.