To successfully diagnose an oral allergy syndrome (OAS) in an individual, a physician will start with a physical examination and a review of the patient’s medical history. A history of allergies – particularly pollen allergies – can help a physician determine whether an oral allergy is present.

While an allergic reaction to pollen is a requirement for anyone suffering from OAS, some people may have such slight pollen reactions that they fail to recognize the condition. In these individuals it is often useful to conduct a skin test. This test involves pricking, scratching or injecting food or pollen extracts into the patient’s skin. The skin will react with redness and swelling for those extracts capable of eliciting an allergic reaction. Skin testing is not 100 percent accurate, however, and results will vary depending on the extract being tested. In addition, skin testing may not be performed in patients with severe allergic reactions.

An elimination diet is sometimes used to verify whether an individual is allergic to a particular fruit, vegetable or nut. This treatment involves removing the foods in question from a patient’s diet to see if the allergic reactions persist. This trial-and-error approach often takes weeks for results, but it can be effective at pinpointing a problem food.

Some other types of allergy tests, including oral challenge tests, are not used in the diagnosis of OAS.