Diagnosis and Differential Diagnosis of Food Allergy

Abstract

Food allergies vary in allergen type, severity, and underlying etiology, making diagnosis challenging. Cross-reactivity between allergens, the presence of multiple food allergies, and food intolerances that often mimic food allergy add additional complexity to the diagnosis. Food intolerances include enzyme and metabolic deficiencies, functional defects, pharmacologic effects, psychosomatic effects, sensitivity to food additives, or reactions to naturally occurring chemicals or toxins in foods. Correct identification of food allergy and causative allergen(s) is important in order to prevent unnecessary dietary restrictions or future allergic reactions. There is currently no single universal method that adequately meets the safety, sensitivity, and specificity required to diagnose a food allergy. The diagnosis of food allergy is primarily based on a combination of clinical history, presence of IgE antibodies, elimination diets, and food challenges. The presence of IgE can be determined by skin prick tests or serum tests, both of which have high sensitivities but low specificities and are associated with a high number of false positives. Currently, the double-blind placebo-controlled food challenge still remains the gold standard for diagnosing an IgE-mediated food allergy, but is resource consuming and carries with it the risk of severe reaction during the challenge.