Food Dependent Exercise Induced Anaphylaxis

Food dependent exercise induced anaphylaxis is anaphylaxis that occurs only when a specific food is eaten within a few hours before exercise. The food alone, or exercise alone, causes no reaction.

Pathophysiology. Exercise lowers the threshold for reaction to a food allergen, probably by increasing gut permeability and allergen absorption and shifting blood flow and mast cell reactivity. Other cofactors include alcohol, aspirin and other non-steroidal anti-inflammatory drugs, heat and infection.

Wheat (omega-5 gliadin, Tri a 19) is the commonest trigger. Others are shellfish, celery, nuts, fruit, milk and egg.

It usually begins in young adults and is more frequent in women.

• Itching, flushing and urticaria during or after exercise
• Angio oedema, throat tightness and wheeze
• Hypotension, collapse and loss of consciousness
• Gastrointestinal symptoms: cramps, vomiting, diarrhoea
• Onset 30 minutes to a few hours after eating
• Recurrent episodes with the same food and exercise combination
• Normal tolerance of the food at rest

• History: meal content and timing, type and intensity of exercise, other cofactors, and a symptom diary.
• Skin prick test and specific IgE to suspected foods and components (omega-5 gliadin for wheat; shellfish tropomyosin; celery). Omega-5 gliadin over 0.35 kUA/L supports the diagnosis in wheat related cases.
• Serum tryptase within 1 to 2 hours of an episode, and a baseline tryptase on recovery to detect mast cell disease.
• Supervised food and exercise challenge: a controlled challenge may be negative despite true disease, so a negative result does not exclude it.
• Cardiac and respiratory assessment to exclude other causes of exercise symptoms.

Differential diagnosis.

• Exercise induced anaphylaxis without a food trigger
• Wheat allergy that reacts at rest
• Cholinergic urticaria
• Idiopathic anaphylaxis
• Mastocytosis and mast cell activation syndrome
• Exercise induced bronchoconstriction, cardiac arrhythmia, vasovagal syncope

• Avoid the trigger food for at least 4 to 6 hours before exercise, and avoid exercise for several hours after eating it. Some patients also need to avoid the food completely.
• Avoid cofactors (alcohol, aspirin and other non-steroidal anti-inflammatory drugs) before exercise.
• Stop exercise at the first symptom, exercise with a companion, and carry adrenaline.
• Anaphylaxis: adrenaline 0.5 mg intramuscularly (children 0.01 mg/kg, maximum 0.5 mg) into the anterolateral thigh, repeated after 5 minutes if no improvement, plus oxygen and intravenous fluids, and observation for at least 6 hours.
• Adrenaline auto injector: 150 microgram for 7.5 to 25 kg, 300 microgram for 25 to 50 kg, 500 microgram for over 50 kg, with a written action plan and training.
• Mild symptoms: cetirizine 10 mg orally once daily in adults (children 1 to 5 years 2.5 mg twice daily; 6 to 11 years 5 mg twice daily). Antihistamine does not prevent anaphylaxis.
• Omalizumab may be used in specialist care for recurrent episodes that cannot be controlled by avoidance.
• Medical alert: a bracelet or card with the diagnosis.

Special groups.

• Athletes and manual workers: individual planning of meals and training schedules is needed.
• Adults with omega-5 gliadin sensitisation: lifelong precautions are likely.

Monitoring. Review every 6 to 12 months. Symptom diary and episode count. Check auto injector dose and expiry.

Referral and escalation. Refer to allergy for any episode of anaphylaxis with exercise. Emergency for collapse, airway swelling or wheeze.