Published online: February 22, 2018
Food-dependent, exercise-induced anaphylaxis is rare type of food allergy. It was first described in 1979 as a case report of shellfish allergy that only manifested itself in the presence of a co-factor, namely exercise. While a number of different foods are reported to be triggers, wheat is reported most frequently. Since affected individuals are often able to tolerate the food in question most of the time and exercise is not the only co-factor, diagnosis is challenging. Omega-5 gliadin, a protein that makes up 3-6% of wheat gluten was identified as the major allergen in 1999 and a test for specific IgE to omega-5 gliadin became available in 2006. This has helped allergists to make a diagnosis without always exposing the patient to the risk and uncertainties of a food challenge.
In their retrospective multicenter study in The Journal of Allergy and Clinical Immunology: In Practice, Kennard et al studied 132 adults with this rare omega-5 gliadin allergy (also known as wheat-dependent exercise-induced anaphylaxis). All patients included in the study had a clinical history of allergic reactions to wheat, with a positive omega-5 gliadin specific IgE, and had been reviewed by an allergist with other allergic causes excluded.
Wheat was correctly suspected by the clinician and/or patient as the allergen in 82% of cases at initial consultation. Exercise was the most common cofactor identified (80%), followed by alcohol (25%), NSAIDs (9%), and heat (5%). There were significant delays to diagnosis of over one year in two thirds of patients, despite the majority of patients presenting with severe anaphylaxis (66%). The data showed no significant difference between the level of the omega-5 gliadin allergy blood test and severity of allergic reaction. Where documented, mast cell total tryptase rose acutely in wheat-dependent, exercise-induced reactions. Of the minority of patients who had blood testing to other cereals, over two-thirds were positive to rye, and roughly one third were positive to each of barley and oat. Regarding management, there was no standardized dietary advice given to patients. Gluten-free diet and avoidance of wheat in combination with exercise yielding the largest reductions in future omega-5 gliadin allergic reactions by 67% and 69% respectively. However, a third of patients still had allergic reactions despite optimal dietary advice.
Omega-5 gliadin allergy is a rare food allergy. To reduce the delay in diagnosis, the authors suggest that adult patients presenting with anaphylaxis of unclear cause should have omega-5 gliadin specific IgE tested at first presentation. They point out that a gluten-free diet or avoiding wheat in combination with exercise (if the cofactor is exercise) helps to significantly decrease the risk of future allergic reactions. However, they advise that antihistamines and an epinephrine auto-injector must always be prescribed alongside dietary advice given the ongoing risk of accidental allergic reactions and the patient informed of the importance of additional co-factors.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.