Oral Allergy Syndrome

Frequently Asked Questions

This document has been developed by ASCIA, the peak professional body of clinical immunology/allergy specialists in Australia and New Zealand. ASCIA information is based on published literature and expert review, is not influenced by commercial organisations and is not intended to replace medical advice.

For patient or carer support contact Allergy & Anaphylaxis Australia or Allergy New Zealand.

ASCIA PC Oral Allergy Syndrome FAQ 202479.50 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. For people with OAS, some raw (uncooked) fresh vegetables, fruits, spices or nuts cause the lips, mouth, tongue and throat to itch, tingle and/or swell.

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

It is rare for an OAS reaction to result in anaphylaxis. However, foods such as kiwi fruit or some tree nuts can cause OAS and food allergy, and eating these foods can sometimes lead to anaphylaxis.

Q 3: Why does oral allergy syndrome (OAS) mainly happen in people with pollen allergy?

OAS is most common in people with asthma or allergic rhinitis (hay fever) who are sensitised to inhaled tree, grass or weed pollens. These pollens have proteins that are similar to (or the same as) those found in some foods, such as vegetables, fruit, spices and nuts. These are known as cross-reactive proteins. In some people with pollen allergy, their immune system confuses a protein in food with a pollen protein, resulting in OAS symptoms.

An example of plant proteins known to cause allergy and OAS are profilins which are found in tree, grass and weed pollens. Profilins are also found in latex and many fruits and vegetables. Allergies to melons, citrus fruits, kiwifruit, tomato and banana can suggest an allergy to profilins.

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

Q 4: What can help reduce oral allergy syndrome (OAS) symptoms?

Ways to reduce OAS symptoms include:

Avoiding the trigger food in its raw, uncooked form (ripe or unripe).
Eating heated, baked, cooked or canned vegetables or fruits (if the food that causes OAS is heated or cooked, the protein is usually destroyed).
Eating peeled vegetables or fruits (the OAS-causing protein is often found in the skin).

Q 5: How is oral allergy syndrome (OAS) diagnosed?

When people with pollen allergy get itching or tingling in the mouth after eating fresh fruit or vegetables, OAS is usually suspected. Skin prick testing for pollen and food allergens (preferably with fresh food) may help with the diagnosis of OAS.

Content updated August 2024

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