Published Online: February 1, 2013
Food allergy affects 4-6% of children in the U.S. and its incidence is increasing. Food allergy is mediated by IgE antibodies, which are bound to mast cells and which, when crosslinked by food antigens, cause the mast cells to release mediators that result in anaphylaxis. Atopic dermatitis (AD) affects more than 15% of children and its incidence is also on the rise. AD and food allergy often coexist. Scratching of dry skin in AD patients breaches the skin barrier, allowing the entry of allergens. Epidemiologic data suggest that the incidence of peanut allergy is increased in children exposed to skin creams containing peanut oils, suggesting that cutaneous sensitization may predispose food allergy.
In an article recently published in The Journal of Allergy and Clinical Immunology (JACI), Oyoshi and colleagues examined the hypothesis that introduction of food antigen through the skin causes IgE-mediated food anaphylaxis. The authors developed a novel mouse model of food allergy by exposing tape stripped mouse skin to egg protein antigen (ovalbumin), which triggers an allergic skin inflammation that shares may features a with AD, and followed it by feeding the mice ovalbumin. This experimental system mimics the situation of a child with eczema who is sensitized to allergen via the skin then develops food anaphylaxis upon ingestion of allergen.
The authors found that mice cutaneously sensitized with ovalbumin developed anaphylaxis following oral challenge with ovalbumin with a rapid drop in body temperature and a rise in the circulating levels of the mast cell protease MCP-1. Anaphylaxis was IgE dependent, because it did not occur in IgE deficient mice. This makes the model highly relevant to IgE-mediated food anaphylaxis in humans. Interestingly, mice whose skin was tape stripped exhibited a marked expansion in the number of mast cells in their small intestine regardless of whether ovalbumin or saline was applied to the injured skin. This demonstrates a cross talk between the skin and the gut, in which mechanical injury to the skin induces expansion in the gut of mast cells which are critical for food anaphylaxis.
The data indicates that the skin may be an important route of sensitization to food antigens. It also suggests that prevention of cutaneous sensitization by allergen avoidance and strategies directed towards restoring skin barrier integrity and limiting gut mast cell expansion may be useful in treating food allergy.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.