Food-induced cutaneous adverse reactions.

The skin is the most frequently affected target organ in allergy or intolerance of food and food additives. The most common manifestation is acute urticaria (with or without angioedema), accounting for 40-60% of patients with IgE-mediated food allergy, whereas food additives rather aggravate chronic urticaria (intolerance provocation). The role of food allergy in the pathogenesis of atopic dermatitis is still controversial; however, there is no doubt that, particularly in infants and young children, food allergens can induce atopic dermatitis or aggravate skin lesions. In adults, food allergy as a cause or a trigger of atopic dermatitis is very rare. However, in food-allergic patients with atopic dermatitis, the ingestion of the food item can provoke the whole spectrum of IgE-mediated symptoms, from oral allergy syndrome to severe anaphylaxis. Skin symptoms can also be induced not only after food ingestion in sensitized people, but also after direct skin contact, as lipophilic food allergens can penetrate the skin via the hair follicles or when the skin barrier function is defective. Immediate contact reactions of the skin are a heterogeneous group: they include not only contact urticaria (contact urticaria syndrome) on an immunologic or nonimmunologic basis, but also allergic or nonallergic eczematous reactions caused by food proteins (protein contact dermatitis). A prototype is baker's eczema in a restricted sense with immediate-type sensitization to flour. Atopic eczema provoked by direct contact of the skin with food must also be taken into consideration. Finally, very rarely, allergic contact dermatitis that is due to type IV sensitization to food or food additives (positive delayed type reaction in the patch tests) can occur. The oral ingestion of these foods may provoke in these patients a generalized eczematous rash or dyshidrosiform reactions (vesicles) of the fingers, palms, and soles.