Exercise-induced anaphylaxis

Did You Know?

• Exercise-induced anaphylaxis is most commonly brought on by aerobic exercise, with jogging cited by 78% of patients in a 1999 study.
• Factors that may increase attack risk include alcohol consumption, pollen exposure, extreme temperatures, NSAIDs, and certain phases of the menstrual cycle.
• The condition is thought to have no link to ethnicity.

Symptoms

Symptoms are divided into mild and severe categories. Mild symptoms include widespread skin flushing, hives, swelling of the body or lips, and nausea or vomiting. Severe symptoms may involve tongue swelling, difficulty swallowing or breathing, airway constriction, feeling faint, and unconsciousness. Most patients report symptom onset within 30 minutes after exercise. An EIA event can progress through four stages: prodromal (redness and itching), early (generalized urticaria), fully developed (gastrointestinal symptoms and airway constriction), and late (frontal headaches and fatigue lasting up to 72 hours).

Food-dependent exercise-induced anaphylaxis

Food-dependent exercise-induced anaphylaxis (FDEIA) is a subcategory in which exercise triggers a reaction only when preceded or followed by ingestion of a specific food allergen. In European countries, common triggers include tomatoes, cereals, and peanuts; in Japan, omega-5-gliadins from wheat are most common. Other reported triggers include shellfish, seeds, dairy (especially cow's milk), fruits and vegetables (such as grapes, onions, and oranges), meats, mushrooms, and the alpha-gal syndrome related to red meat. Ingestion typically occurs minutes to hours before exercise, though attacks have occurred when food is consumed shortly after activity. One theory suggests that exercise-induced acidic pH changes in muscles and serum increase mast cell degranulation; a study found that patients given the antacid sodium bicarbonate before exercise did not experience symptoms.

Pathophysiology

The pathophysiology of EIA and FDEIA is not fully understood. Histamine levels in blood plasma are elevated during attacks, and mast cells in the skin show morphological changes after exercise similar to those seen in atopic patients after allergen exposure. One theory proposes that increased gastrointestinal permeability during exercise enhances contact between allergens and the gut immune system; a study found that wheat-dependent EIA patients had omega-5-gliadins in their sera only after both exercise and wheat ingestion. Another theory suggests that exercise and aspirin may activate tissue transglutaminase in intestinal mucus, which cross-links omega-5-gliadins into larger peptide aggregates that increase IgE binding. A third theory involves blood redistribution during exercise: food-sensitized immune cells normally confined to the gut circulation may shift to the skin or skeletal muscles, where mast cells differ structurally and can be induced by food allergens. A 2010 study showed that food allergens were tolerated by intestinal mast cells at rest but not after exercise.

Treatment

If exercise is stopped at the first sign of symptoms, improvement usually occurs within minutes without further treatment. Common treatments include regular antihistamines, use of an epinephrine injector, and avoidance of exercise. In a 1999 study, 56% of patients reported using antihistamines and 31% had used epinephrine. Behavioral changes were also common: 44% avoided exercise in extreme temperatures, 37% avoided trigger foods, 36% refrained during allergy season, and 33% avoided high humidity.