Role and significance of atopy patch test

Abstract

Atopic eczema/dermatitis syndrome (AEDS) is a chronic, intermittent, inflammatory, genetically predisposed skin disease characterized by severe pruritus and xerosis. AEDS is a common disorder in children with an increasing prevalence. A number of environmental factors have been implicated in the pathogenesis of AEDS. Atopy patch test (APT) is a patch test using type Iota allergens known to elicit IgE mediated reactions. Results are evaluated after 48 and 72 h. APT has been recognized as a useful diagnostic tool in the diagnosis of delayed type of reaction in AEDS since specific IgE (sIgE) and skin prick test (SPT) can be only correlated with early reactions. Standardized technique has been proposed by the European Task Force on Atopic Dermatitis. It consists of purified allergen preparation in petrolatum, applied in 12 mm diameter Finn chambers mounted on Scanpor tape to non-irritated, non-abraded, or tape-stripped skin on the upper back. Optimal results were obtained with petrolatum, in aeroallergen concentration over 5000 PNU. Food allergy takes place in the first years of life, while the role of aeroallergens becomes more significant in older children and adults. A common scenario is development of allergy to cow's milk early in life, usually accompanied by allergy to hen's egg and wheat. Up to 3 years of age, the child usually becomes tolerant to food and sensitization to one of multiple aeroallergens occurs. The children that will develop clinically relevant reactions to food may benefit from elimination diets. APT has been recognized as a diagnostic tool in food allergy evaluation, but its role remains controversial and double blind placebo controlled food challenge remains the gold standard. It has a role in the detection of gastrointestinal manifestations of allergy and in eosinophilic esophagitis. When the symptoms occur at air-exposed sites, the role of aeroallergens is possible. Today, the most commonly used aeroallergens are house dust mite, pollen and animal dander.