Wheat Allergy

Wheat allergy is an IgE-mediated reaction to wheat proteins. It includes classic food allergy in children, wheat dependent exercise induced anaphylaxis, and baker's asthma, and must be separated from coeliac disease and non-coeliac gluten sensitivity.

Pathophysiology. Wheat allergens include albumins and globulins, gliadins (including omega-5 gliadin, Tri a 19) and glutenins. Omega-5 gliadin sensitisation is linked to severe reactions and to exercise as a cofactor. Inhaled flour allergens cause baker's asthma through a different route.

Most children with wheat allergy outgrow it by adolescence. Adults with omega-5 gliadin allergy tend to persist.

Wheat allergy is not a gluten specific disorder: reactions may occur to non-gluten proteins.

• Urticaria, angio oedema, vomiting and diarrhoea within 2 hours of eating wheat
• Wheeze and rhinitis
• Anaphylaxis, in particular with exercise, alcohol or aspirin as cofactors (wheat dependent exercise induced anaphylaxis)
• Atopic dermatitis in infants
• Baker's asthma and rhinitis in flour workers
• Eosinophilic oesophagitis in some children
• Delayed gastrointestinal symptoms in non-IgE disease

• History: wheat product, quantity, time to onset, and cofactors (exercise, alcohol, non-steroidal anti-inflammatory drugs, infection).
• Skin prick test and specific IgE to wheat and omega-5 gliadin: omega-5 gliadin positivity identifies adults at risk of wheat dependent exercise induced anaphylaxis. Wheat IgE alone has a low positive predictive value, and cross-reactive grass pollen sensitisation causes false positives.
• Supervised oral food challenge, sometimes with exercise, when the diagnosis is uncertain.
• Coeliac disease screen: tissue transglutaminase IgA with total IgA, on a gluten containing diet, if gastrointestinal symptoms are chronic.
• Baker's asthma: spirometry, peak flow monitoring and specific IgE to flour.

Differential diagnosis.

• Coeliac disease
• Non-coeliac gluten sensitivity and irritable bowel syndrome
• Grass pollen cross-reactivity (false positive tests)
• Other food allergy (cow's milk, egg, soy)
• Food dependent exercise induced anaphylaxis from other foods
• Eosinophilic oesophagitis

• Avoidance of wheat. Rye, barley and oats cross-react in a minority and can often be eaten after testing. A gluten free diet is not equivalent to a wheat free diet, since some gluten free foods contain wheat starch.
• 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.
• 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.
• Mild reactions: 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).
• Wheat dependent exercise induced anaphylaxis: avoid wheat for 4 to 6 hours before exercise and for a period after, or avoid wheat entirely if reactions occur without exercise; avoid alcohol and aspirin and other non-steroidal anti-inflammatory drugs near exposure; never exercise alone.
• Baker's asthma: remove from exposure early, and manage asthma with inhaled corticosteroid and bronchodilator in the usual way.
• Reintroduction in children: supervised challenge every 12 months after 1 to 2 years of avoidance, with baked wheat as an early stage.
• Dietitian review to preserve intake of fibre, B vitamins and iron.

Special groups.

• Children with wheat allergy: most outgrow it, so avoid unnecessary long term elimination.
• Adults with omega-5 gliadin sensitisation: lifelong precautions are likely.

Monitoring. Growth in children. Review every 6 to 12 months. Check auto injector dose and expiry. Spirometry in baker's asthma.

Referral and escalation. Refer to allergy for anaphylaxis, wheat dependent exercise induced anaphylaxis, or occupational asthma. Emergency for anaphylaxis.