Epicutaneous exposure to protein antigen and food allergy

Background The aetiology of food allergy remains unclear. Although failure to develop or breakdown in oral tolerance has been proposed, the existence of physiologic sensitization routes other than the gastrointestinal tract cannot be excluded. Objective The purpose of this study is to clarify whether or not exposure to allergen through the skin can promote food allergy. Methods BALB/c mice were shaved on the back, and a patch impregnated with 100 mug of ovalbumin (OVA) was applied to the dorsal skin for a 1-week period and then removed. After three courses of sensitization, OVA-specific antibodies in sera were measured, and then mice were orally challenged with 50 mg of OVA. Anaphylactic symptoms, plasma histamine levels, and histology of intestines and lungs after oral challenge were examined. Results Epicutaneous (EC) sensitization of mice to OVA induced a high level of OVA-specific IgE. Subsequent oral challenge with OVA resulted in symptoms of systemic anaphylaxis with elevated levels of plasma histamine as well as histological changes in both intestines and lungs. In the presence of anti-IL-4 antibodies, EC sensitization failed to provoke an IgE response, but still induced a Th2-predominant cellular immune response in lungs after oral challenge. Conclusion We demonstrated for the first time that food allergy can be induced by allergen exposure through the skin. Our results identify a novel role of EC sensitization in the pathogenesis of food allergy.