2020 Volume 34 Issue 1 Pages 45-51
Oral allergy syndrome (OAS) is a form of localized IgE-mediated allergy, usually to fruits or vegetables, confined to the lips, mouth, and throat. This syndrome most commonly affects patients who are allergic to pollens, especially birch pollen. So, it's also referred to as pollen-associated food allergy syndrome (PFAS). Because birch pollen allergen, Bet v 1, and the homologous protein of apple, Mal d 1, have 56% identities in amino-acid sequence, these two allergens are cross-reactive through the conserved part which are thought to be conformational epitopes. Accordingly, causal allergens are usually heat-labile. Most common causal foods are raw fruit/vegetables and cooked forms are tolerated.
There are some exceptional cases. Soy protein-containing food items can cause a severe allergic symptom (face swelling, feeling of narrowing of the throat, difficulty swallowing, urticaria, wheezing) in patients with birch pollen allergy, and Bev 1 homologous protein, Gly m 4, is considered as the causal allergen.
In this text, we explain the basic mechanism of PFAS in an easy-to-understand manner, and introduce another hypothesis as to why soymilk cause severe allergy in birch pollen sensitive patients. Recently, the relationship between cypress pollen and peach GRP has been reported overseas, and we report the proportion of positive reactions to peach-GRP in Japanese cedar pollen patients.
