The 'atopy patch test' in evaluating the role of aeroallergens in atopic eczema

The atopy patch test (APT) is a procedure involving epicutaneous patch tests with allergens known to elicit IgE-mediated reactions and the evaluation of eczematous skin lesions. APT can be performed on normal uninvolved skin without artificial manipulations such as tape stripping or use of irritants. APT has been standardized regarding the use of vehicle and dose response relationships. In several studies, approximately two thirds of patients with atopic eczema (AE) showed positive APT reactions to aeroallergens, most frequently to house dust mite. Positive APT reactions were significantly more frequent in patients with a typical air-exposed eczematous distribution pattern. Using evaporimetry to study transepidermal water loss, allergen-induced disturbance of epidermal barrier functions was found to be significantly more pronounced on APT reactions compared to classical contact allergy patch test sites in the same individual. It has been shown that with APT eczematous skin lesions can be elicited by skin contact with aeroallergens, at least in a subgroup of patients with AE, and thereby, that IgE-mediated allergy does play a role in the etiopathophysiology of this disease. Future studies should help to bring this test into clinical routine in order to establish an equivalent for 'skin provocation' comparable to nasal and bronchial provocation tests in respiratory allergy.