How to use serum-specific IgE measurements in diagnosing and monitoring food allergy

Hypersensitivity (adverse reaction) to a food can be broadly divided into allergic hypersensitivity (food allergy) and non-allergic hypersensitivity (food intolerance).1 Food allergy is defined as an adverse immune response to a food allergen, whereas food intolerance is generally non-immune mediated. Food allergy can be subdivided into two main categories: IgE-mediated and non–IgE-mediated food allergy. The differences between the two are shown in table 1. Food intolerance incorporates several other adverse reactions to foods. These include toxic contaminants in food (eg, histamine in scombroid fish poisoning), pharmacological properties (eg, tyramine in aged cheese or caffeine), host characteristics (eg, lactase deficiency) and food aversion. View this table: Table 1 Differences between IgE- and non–IgE-mediated food allery7 13 Food allergies are common in the paediatric population, with up to 8% of young children affected by IgE-mediated reactions.2,–,4 Furthermore, up to a third of parents report their child having a food-related problem within the first 3 years of life, although many prove not to have food allergy.5 Health professionals working with children will therefore regularly encounter suspected adverse reactions to food, including food allergy, and therefore need to understand how to evaluate this problem.6 Medical history is essential and is often the most helpful diagnostic modality. It ultimately aims to identify whether an allergic food reaction has occurred and identify the most likely allergens to direct testing. Box 1 shows vital questions in establishing whether the adverse reaction to food may be IgE mediated. ### Box 1 Important information to extract from the history31 1. The food responsible for the reaction 2. The quantity of suspected food ingested 3. The length of time between ingestion and development of symptoms (<2 h if IgE-mediated food allergy) 4. Whether similar symptoms occurred when the food was eaten previously 5. Whether other factors (eg, exercise) are necessary 6. When the last reaction to the food occurred A diagnosis …