The diagnosis of food allergy

Food allergy is increasingly common; however, there is a discrepancy between the large number of people who believe they or their children are affected and the actual number with true food allergies. It is therefore imperative that physicians evaluating patients with possible adverse reactions to foods understand the current modalities used to diagnose food allergies.

Simple tests including skin-prick testing (SPT) and serum food-specific IgE testing are the most commonly used diagnostic tests to evaluate for IgE-mediated food reactions. However, these tests have pitfalls and their usefulness must be appreciated to avoid over- and underdiagnosis.

A firm diagnosis is imperative because a misdiagnosis could lead to life-threatening reactions and overdiagnosis will lead to unnecessary elimination diets with nutritional and social implications. Physician-supervised oral food challenges (OFC) remain the gold standard for food allergy diagnosis; however, a careful medical history and simple tests can often provide a reliable diagnosis.

In this review, we examine the usefulness and pitfalls of SPT used by allergists and serum food-specific IgE levels that are available to all practitioners. We also review the OFC as a diagnostic modality in food allergy. Finally, we describe emerging tests, such as the basophil activation test, atopy patch testing, and component-resolved diagnostics, that may be of benefit in the future.