What are the characteristics of pollen food syndrome?

Features of Pollen Food Syndrome

Pollen food syndrome (PFS), also known as oral allergy syndrome (OAS), is characterized by immediate allergic reactions in the mouth and throat after consuming certain raw plant foods in individuals who are sensitized to specific pollens, with symptoms typically limited to the oral cavity but occasionally causing systemic reactions including anaphylaxis. 1

Key Clinical Features

Symptoms

• Primary symptoms (most common):
  • Itching or tingling of lips, tongue, palate, and throat
  • Swelling of lips, tongue, and oral mucosa
  • Numbness of the mouth or lips
  • Symptoms typically occur within minutes of food consumption 2, 3

Pathophysiology

• Caused by cross-reactivity between pollen allergens and structurally similar proteins in fruits and vegetables
• Mediated by IgE antibodies that recognize both pollen and food allergens
• Common cross-reactive proteins include:
  • PR-10 proteins (Bet v 1 homologs)
  • Profilins
  • Lipid transfer proteins 2, 4

Common Associations

• Pollen-food relationships:
  • Birch pollen: apple, pear, cherry, peach, plum, apricot, kiwi, hazelnut, almond, carrot, celery, potato
  • Grass pollen: melon, watermelon, orange, tomato
  • Ragweed pollen: banana, melon, cucumber, zucchini 1, 5
• Most common prototype: birch-apple syndrome 2
• Affects 30-60% of individuals with pollen allergies 2

Risk Factors

• Pre-existing seasonal allergic rhinitis or asthma
• Pollen sensitization
• Geographic location (related to prevalent pollen types) 3, 4

Diagnostic Considerations

• Diagnosis primarily based on characteristic clinical history
• Confirmatory testing may include:
  • Skin prick tests to identify sensitization to specific pollens and foods
  • Serum-specific IgE testing
  • Oral food challenges (in ambiguous cases) 1, 5

Important Clinical Distinctions

• PFS vs. true food allergy:

  • PFS symptoms typically limited to oral cavity
  • True food allergies more commonly cause systemic reactions
  • PFS reactions usually occur only with raw foods; cooked/processed forms often tolerated 1

• Risk of systemic reactions:

  • While most reactions are mild and localized, systemic reactions including anaphylaxis can occur
  • Higher risk with concentrated forms (smoothies, juices) and certain foods (particularly nuts) 6, 5

Management Approaches

• Avoidance strategies:

  • Avoid raw trigger foods
  • Cooked or processed forms of trigger foods are usually tolerated as heating denatures the allergenic proteins
  • Commercially processed and pasteurized products are generally safer than fresh 1

• Medication:

  • H1 antihistamines can be taken before consuming potential trigger foods
  • For isolated mild symptoms, antihistamines alone are appropriate
  • Epinephrine auto-injectors generally not required unless history of systemic reactions 1

• Nutritional considerations:

  • Avoid unnecessary dietary restrictions
  • Nutritional counseling may be needed, especially with multiple food avoidances 1

• Follow-up:

  • Seek allergy re-testing if symptoms change or worsen over time 1

PFS can significantly impact quality of life despite typically mild symptoms, as anxiety about reactions to new foods and dietary restrictions can be challenging for patients, particularly those following vegetarian or vegan diets 5.