Oral allergy syndrome is a type of food allergy which mainly affects people with springtime hay fever. It is caused by a cross-reaction, between antibodies to pollens, usually birch tree pollen, and allergens in many different plant foods. It is characterised by symptoms of itching and/or swelling in the mouth and/or throat when eating certain fruits vegetables and nuts. Many of the allergens causing OAS are destroyed by heat, making allergy testing using traditional allergen extracts unreliable. Prick testing or challenging with fresh foods is more reliable, but time consuming, inconvenient and largely unavailable. Pilot study results suggest the characteristic symptoms and foods involved in OAS allow accurate diagnosis using clinical history alone, which forms the basis for the hypothesis of this proposal that OAS can be diagnosed accurately by use of a validated questionnaire alone. The diagnostic questionnaire (PFSDQ), revised from the results of the pilot study, will be tested against two reference test methods, the gold standard of oral food challenge, and the 'platinum standard' of diagnosis made by a medical expert based on history, skin prick testing and oral food challenge. This is not an epidemiological study but with no published studies on OAS in a UK population, this study will also provide some information on the prevalence of OAS in those with springtime hayfever in the UK.