Pollen-Food Allergy Syndrome
Pathology: The immune system produces IgE against an environmental protein (e.g., plant pollen), which manifests as hay fever. Plant foods (such as fruit, vegetables, nuts, etc.) with similar proteins can result in swelling, redness and itching around the mouth and face.
Food-Symptom Interval: Symptoms usually occur within minutes to a few hours after eating.
Diagnosis: There are no laboratory tests to diagnose pollen-food syndrome directly.
Treatment: The food allergen is entirely responsible for the symptoms. The patient will not have symptoms if they avoid the allergen.
This condition starts with pollen allergy. The immune system produces IgE directed against an epitope within a pollen protein (i.e., the individual is sensitized to the pollen). IgE attaches to mast cells in the respiratory system and throughout the body. When pollen is inhaled, the mast cells activate and release inflammatory chemicals, causing hay fever symptoms. If a pollen-allergic individual eats a plant food with a homologous (similar) protein, their oral mast cells activate and release inflammatory chemicals into the surrounding area (cross-reactivity). The localized inflammation leads to oral itching, tingling, redness and swelling. Luckily, heat can break down plant food proteins (denatured). The video gives a visual example.
Typically, pollen-food allergy syndrome is limited to hay fever symptoms. However, the distal regions of the gastrointestinal tract may also become inflamed. In rare cases, it can lead to systemic allergic symptoms, including anaphylaxis.
Each plant pollen has a long list of potentially cross-reactive plant food proteins. However, reactions are individual, and food avoidance should be based on the individual’s history with the food. Patients often unnecessarily avoid the entire list of potentially cross-reactive proteins.
Pollen-food allergy syndrome is one example of cross-reactivity. Others include latex cross-reactive foods and dust mite/shrimp allergy.
Pollen-food allergy syndrome is diagnosed by an allergist based on their history and laboratory tests to confirm pollen allergies.