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Pathogenesis of oral allergy syndrome (pollen-food allergy syndrome)

Anna Nowak-Węgrzyn, MD
Section Editor
Scott H Sicherer, MD, FAAAAI
Deputy Editor
Anna M Feldweg, MD


Pollen-food allergy syndrome (PFAS) describes allergic reactions, usually limited to the oropharynx, which occur upon ingestion of certain fresh fruits, nuts, or vegetables in individuals who are sensitized to plant pollens [1,2]. These reactions are a form of immunoglobulin E (IgE)-mediated hypersensitivity. The causative allergens in these plant foods are homologous to pollen allergens [3,4]. The disorder is also called "pollen-food syndrome" and "pollen-associated food allergy syndrome" [5].

Oral allergy syndrome (OAS) is a term used variably as a synonym of PFAS or to describe just the isolated oropharyngeal symptoms caused by pollen-related foods. In this review, OAS is applied to isolated oropharyngeal symptoms.

The symptoms of OAS result from contact urticaria of the oropharynx. Symptoms are usually limited to the mouth and throat and only observed with raw forms of the food because the causative allergens are rapidly inactivated by digestion and cooking, although this is not uniformly true. Systemic reactions as well as reactions to cooked foods are observed in a small proportion of patients.

This topic review will present the pathogenesis of PFAS. The clinical manifestations, risk factors, diagnosis, and management of PFAS are presented elsewhere. (See "Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)" and "Management and prognosis of oral allergy syndrome (pollen-food allergy syndrome)".)


Fruit and vegetable allergens are highly conserved and share varying degrees of homology with allergens from other fruits and vegetables as well as pollens. This structural and functional homology underlies the extensive cross-reactivity observed clinically [6-8].


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Literature review current through: Sep 2016. | This topic last updated: Sep 1, 2016.
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