Pollen-Associated Food Reactions (Pollen-Food Allergy Syndrome)

Definition and Mechanism

Pollen-food allergy syndrome (PFAS) is a hypersensitivity reaction to raw plant-based foods that occurs in individuals already sensitized to cross-reacting pollen allergens, manifesting primarily as itching of the lips, tongue, and mouth, according to the American Academy of Allergy, Asthma, and Immunology 1, 2

Symptoms are typically limited to the oral cavity and pharynx, occurring within minutes of consuming raw plant foods, and can sometimes progress to or overlap with more severe systemic allergic reactions, including anaphylaxis, as noted by the American Academy of Allergy, Asthma, and Immunology 1, 2

Birch pollen sensitization is associated with reactions to fruits such as apple, pear, plum, cherry, peach, and apricot, as well as vegetables like celery and carrots, and nuts including hazelnuts and almonds, as reported in the Journal of the American Academy of Dermatology 3
Other tree pollens, such as alder pollen, have similar cross-reactions to birch, according to the American Academy of Allergy, Asthma, and Immunology 4

Cooked or processed forms of trigger foods are typically tolerated because the heat-labile proteins are destroyed during cooking, as noted by the American Academy of Allergy, Asthma, and Immunology 5, 6, 7
Patients with PFAS often tolerate baked goods containing the trigger food, cooked fruits and vegetables, and canned or processed versions of the food, as reported in the Journal of Allergy and Clinical Immunology 5, 6, 7

The allergist-immunologist should evaluate these reactions to determine the cause, advise which foods to avoid, identify other potential problematic foods, and assess risk for severe reactions, according to the American Academy of Allergy, Asthma, and Immunology 1, 2
Standard testing includes skin prick tests and serum food-specific IgE, though these must be interpreted in clinical context, as noted by the American Academy of Allergy, Asthma, and Immunology 1, 2

Treatment primarily involves avoiding trigger foods in their raw form, with the extent of avoidance guided by the specific sensitization profile and reaction history, as reported in the Journal of Allergy and Clinical Immunology 5, 6, 7
Patients should be counseled that while most reactions remain localized, progression to systemic symptoms can occur, according to the American Academy of Allergy, Asthma, and Immunology 1, 2
Seasonal variation in symptom severity may occur, correlating with pollen exposure, as noted by the American Academy of Allergy, Asthma, and Immunology 4

The allergens responsible for oral allergy syndrome, particularly Bet v 1 homologous proteins in apples (Mal d 1), are exquisitely sensitive to heating and processing methods, according to the American Academy of Allergy, Asthma, and Immunology 8, 9
Commercial apple juice undergoes pasteurization, which denatures these unstable allergens, allowing most OAS patients to consume it, as recommended by the American Academy of Allergy, Asthma, and Immunology 8, 9

These proteins are unstable and sensitive to heating and processing methods like freeze-drying, which destroys the allergens, as stated by the European Academy of Allergy and Clinical Immunology 8, 9
Fresh-pressed, unpasteurized apple juice or cider may still contain active allergens and could trigger symptoms, highlighting the importance of proper processing, according to the American Academy of Allergy, Asthma, and Immunology 8, 9

Variety, ripeness of the fruit, and storage method may influence the amount of relevant allergen, which can impact the safety of apple products for OAS patients, as noted by the European Academy of Allergy and Clinical Immunology 8, 9