Clinical manifestations of food allergy

Food allergy is defined as an adverse reaction because of an abnormal immunological response to food protein. The immune pathogenesis is, in the majority of cases, IgE-mediated although it may also be cell-mediated (non-IgE) or mixed IgE/cell-mediated. Food allergy affects as many as 2 to 8% of young children and the presentation can be highly variable. There is usually a clear temporal relationship between food exposure and the development of allergic symptoms. At times, symptoms may develop hours or days after food exposure making the diagnosis difficult. Food allergy usually presents as multi-system involvement, most commonly gastrointestinal symptoms which occur with a frequency of 50 to 80% of cases. These are followed by cutaneous symptoms and respiratory symptoms, occurring in 20 to 40%, and 4 to 25% of cases, respectively. Gastrointestinal manifestations include oral allergy syndrome, gastrointestinal anaphylaxis, allergic eosinophilic esophagitis, allergic eosinophilic gastroenteropathy, food protein-induced enteropathy, food protein-induced enterocolitis syndrome, food protein-induced proctocolitis, gluten-sensitive enteropathy, infantile colic, irritable bowel syndrome, and constipation. Cutaneous manifestations are urticaria/angioedema, atopic dermatitis, contact dermatitis, and dermatitis herpetiformis. Rhinitis/rhinoconjunctivitis, asthma, Heiner syndrome, and serous otitis media are the respiratory manifestations of food allergy. Other manifestations include systemic anaphylaxis, food-dependent exercise-induced anaphylaxis, migraine, epilepsy, diabetes mellitus, nephrotic syndrome, nocturnal enuresis, anemia, thrombocytopenia, vasculitis, and arthropathy/arthritis. This chapter discusses the various clinical manifestations of food allergy.