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Oral Allergy Syndrome

Frequently Asked Questions (FAQ)

pdfASCIA PCC Oral Allergy Syndrome FAQ 202151.68 KB

Q 1:  What is Oral Allergy Syndrome (OAS)?

Oral allergy syndrome (OAS), also known as pollen food syndrome, is a type of food allergy with symptoms that usually affect the lips, mouth, tongue and throat. People with OAS find that some raw (uncooked) fresh vegetables, fruits, spices or nuts will make their lips, mouth, tongue and throat itch, tingle or swell.

Q 2: Can OAS result in severe allergic reactions (anaphylaxis)?

Yes, however this is rare. Some foods which commonly cause OAS can also cause food allergy, such as kiwi fruit or some tree nuts, and this can sometimes progress to anaphylaxis.

Q 3: Why does OAS mainly occur in people with pollen allergy?

OAS most commonly occurs in people with asthma or allergic rhinitis (hay fever) who are sensitised to inhaled tree, grass or weed pollens, which contain proteins that are similar to proteins found in foods.

Some pollen and food allergens share common allergenic proteins, which are known as cross reactive proteins. This means that in some people with pollen allergy, their immune system confuses a food protein with a pollen protein, resulting in OAS.

Pollen allergy usually develops before OAS, and OAS symptoms may be worse when there is a lot of the pollen you are allergic to in the air.

An example of plant proteins that are known to cause allergy and OAS are profilins, which are found in trees, grass and weed pollens as well as latex and many fruits and vegetables. Allergies to melons, citrus fruits, tomato, and banana or a combination of these suggest an allergy to profilins.

Q 4: Can people with OAS usually eat foods if they are cooked?

Yes. If the food is heated or cooked, the protein is usually destroyed, as the cross-reactive proteins in pollens and foods are often fragile. Ways to reduce OAS symptoms include:

  • Avoiding the offending food in their raw, uncooked form (ripe or unripe).
  • Eating heated, baked, cooked or canned vegetables or fruits.
  • Eating peeled vegetables or fruits, as the OAS-causing protein is often found in the skin of the produce.

Q 5: How is OAS diagnosed?

In people with pollen allergy, itching or tingling in the mouth after eating fresh fruit or vegetables is usually enough to suspect OAS. Diagnosis of OAS may be confirmed by skin prick testing for pollens and food allergens, preferably using fresh food for skin prick testing.

Q 6: Where can further information and support be obtained?

© ASCIA 2021

Content updated September 2021

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ASCIA is the peak professional body of clinical immunology/allergy specialists in Australia and New Zealand.

ASCIA resources are based on published literature and expert review, however, they are not intended to replace medical advice. The content of ASCIA resources is not influenced by any commercial organisations.