What causes oral allergy syndrome?
Fresh fruit, vegetables and nuts are common causes of oral allergy syndrome. Some patients are allergic to a wide range of these foods. There are well-recognised groups of these foods which can cause symptoms. The key to oral allergy syndrome is the association of groups of food allergies with seasonal allergic rhinitis or ‘hayfever’. It has been shown that pollens from trees (especially Birch), grasses and weeds contain proteins of similar structure to those present in certain fruit, vegetables, nuts and spices. These proteins are recognised by the immune system of a person with hayfever and can trigger an allergic reaction in a susceptible person when they eat a food which shares the same protein as the pollen. The most well-recognised cross-reactions occur with allergy to tree pollens, and are shown in the table below. The associations with grass pollen are less clear cut and a specific “syndrome” has not been described. It is important to recognise that some people have more seriou