Oral Allergy Syndrome, Cross-reacting Allergens and Co-occurring Allergies

Oral allergy syndrome (OAS) is a complex of clinical symptoms in the mucosa of the mouth and throat, that result from direct contact with food allergens in an individual who also exhibits respiratory allergy to inhaled allergens, usually pollens, and especially birch pollen. Symptoms include itching and irritation of oral tissues, swelling of the lips, tongue, and sometimes papules or blistering of these tissues. Because many systemic allergic reactions start with oral symptoms, confusion and concern have arisen regarding the limitations and application of this definition of the syndrome, and the degree to which cross-reacting food should be avoided in individuals with pollen allergy. Profilins and pathogenesis-related proteins, common to many plants that are botanically unrelated have been identified as allergens responsible for OAS. Latex allergy and its associated food allergy is another example of cross-reacting allergens in botanically unrelated plants; in this case the component responsible has been identified as a hevamine. In the management of food allergy, the subject of cross-reactivity of allergens is becoming increasingly complex. This review examines the problems of OAS, cross-reacting allergens and co-existing allergies in light of recent research into the characteristics of allergens and the factors that predispose to food allergy. Some suggestions are provided for the application of this information in the clinical setting.