Peter Forshaw, a retired lorry mechanic from southeast London, experienced a frightening episode during a football match at age 43 when he suddenly collapsed, gasping for air. Initially suspected to be a heart attack, tests ruled this out, and he was discharged without a diagnosis. Years later, after another severe reaction while performing physically demanding work, Forshaw was diagnosed with exercise-induced anaphylaxis, a rare condition where physical exertion elevates his heart rate above resting levels, provoking a potentially life-threatening allergic response.
Anaphylaxis is a severe, systemic allergic reaction that can be triggered by various factors, including foods, insect bites, and exercise. According to Dr. Scott Pereira, a consultant immunologist, the immune system overreacts, releasing chemicals like histamine that cause blood vessels to widen and leak, leading to flushing, hives, and swelling. These chemicals also constrict airways, making breathing difficult, and can cause gastrointestinal distress and a drop in blood pressure, leading to collapse.
In exercise-induced anaphylaxis, the reaction is typically provoked by a food in combination with exercise. The most common culprit is a protein called omega-5 gliadin found in wheat, though shellfish, nuts, celery, and tomatoes have also been implicated. Forshaw's reactions were later linked to wheat and sulfites. Crucially, individuals with this condition can often consume these foods without issue when resting, but the combination with exercise triggers the severe response. Dr. Pereira explains that exercise can make the gut wall temporarily more permeable, allowing larger amounts of food proteins to enter the bloodstream. Exercise also redistributes blood flow and raises body temperature, which can destabilize immune cells.
While exercise-induced anaphylaxis often begins in adolescence or young adulthood, it can occur at any age. Diagnosis can be challenging because exercise is only one factor. Other co-factors, such as alcohol, non-steroidal anti-inflammatory drugs (NSAIDs), infections, high pollen counts, and hormonal changes, can lower the threshold for a reaction. These factors can accumulate with age, potentially increasing the risk.
Forshaw's initial incident occurred in 2008, but it wasn't until 2014, after another attack while changing a truck axle, that he received a diagnosis. Initially misdiagnosed with atrial fibrillation, subsequent extensive allergy testing revealed his wheat and sulfite allergies and the exercise-induced nature of his anaphylaxis. This diagnosis meant even a brisk walk could be life-threatening.
Following diagnosis, individuals are advised to avoid trigger foods for a significant period before exercising, typically four to six hours, to allow food proteins to clear the bloodstream. Many are also prescribed adrenaline auto-injectors, such as EpiPens, for emergency use. Despite these precautions, Forshaw experienced another severe reaction in 2022 after running to catch a train. He was forced to use his EpiPen and collapsed, requiring an ambulance. He now carries two EpiPens and carefully manages his diet and activity, avoiding wheat for several hours before and after gentle exercise, a condition that significantly impacts his daily life, including travel and physical mobility.