Pollen Food Allergy Syndrome

Pollen food allergy syndrome (oral allergy syndrome) causes itching and tingling of the mouth and throat within minutes of eating raw fruit, vegetables or nuts in people sensitised to pollen. It is the commonest food allergy in adults, and symptoms are usually mild.

Pathophysiology. IgE antibodies made against airborne pollen proteins cross-react with similar proteins in plant foods. These proteins (Bet v 1 homologues, profilin) are broken down by heat and digestion, so cooked foods are usually tolerated and systemic reactions are uncommon.

Birch pollen is the commonest cause, with cross-reactivity to apple, pear, cherry, peach, hazelnut, almond, carrot, celery and kiwi. Grass pollen links to melon, tomato and peanut, and ragweed pollen links to melon and banana.

Lipid transfer protein (Pru p 3, in peach) sensitisation behaves differently, with systemic reactions to cooked foods.

• Itching and tingling of the lips, tongue, palate and throat within minutes, lasting under 30 minutes
• Mild lip or tongue swelling
• Worsening in the pollen season
• Occasional urticaria, abdominal pain, or wheeze
• Rare anaphylaxis, in particular with lipid transfer protein sensitisation or with exercise or alcohol as cofactors
• Seasonal allergic rhinoconjunctivitis

• History: foods causing symptoms, relation to raw or cooked foods and to pollen seasons.
• Skin prick test with pollen extracts and fresh food (prick-to-prick) supports the diagnosis.
• Specific IgE to pollen and components: Bet v 1 (birch), Bet v 2 (profilin) and Pru p 3 (lipid transfer protein). Pru p 3 positivity signals risk of systemic reactions.
• Oral food challenge is rarely needed.

Differential diagnosis.

• Primary food allergy (peanut, tree nut)
• Lipid transfer protein syndrome
• Latex fruit syndrome
• Eosinophilic oesophagitis
• Irritant reaction to acidic fruits
• Alpha gal syndrome and other causes of oral symptoms

• Reassurance: most reactions are limited to the mouth and settle quickly.
• Avoid trigger foods raw, or eat them cooked, canned, microwaved or peeled, which destroys or removes the allergen. Do not avoid all fruit and vegetables unnecessarily.
• 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), taken before exposure or after symptoms.
• Systemic or severe reactions (lipid transfer protein or cofactor related): adrenaline 0.5 mg intramuscularly (children 0.01 mg/kg, maximum 0.5 mg) and an auto injector prescribed by weight (150 microgram for 7.5 to 25 kg, 300 microgram for 25 to 50 kg, 500 microgram for over 50 kg). Advise avoiding cofactors (exercise, alcohol, aspirin and other non-steroidal anti-inflammatory drugs) near exposure.
• Allergen immunotherapy for birch pollen (sublingual tablet 12 SQ-Bet once daily, starting 12 to 16 weeks before the season and continued for 3 years) can reduce pollen symptoms and may lessen food symptoms in some patients.
• Treat seasonal rhinoconjunctivitis with a non-sedating antihistamine and intranasal corticosteroid.

Special groups.

• Children and adolescents: symptoms may start with the first hay fever seasons.
• Patients with prior systemic reactions to a food: refer for assessment of primary allergy.

Monitoring. Review every 12 months, and sooner if symptoms spread to cooked foods or become systemic.

Referral and escalation. Refer to allergy for systemic reactions, reactions to cooked foods, multiple nut reactions, or when immunotherapy is considered. Emergency for anaphylaxis.