Oral Allergy Syndrome (OAS)

This article has been reviewed by Thanai Pongdee, MD, FAAAAI

If you suffer from allergic rhinitis (hay fever), your mouth or throat may become itchy after eating an apple or celery.


Cross-reactivity happens when the immune system thinks one protein is closely related to another. In the case of allergic rhinitis and foods, the result is called oral allergy syndrome (OAS).


Rarely, OAS can cause severe throat swelling or even a systemic reaction, called anaphylaxis (an-a-fi-LAK-sis), in a person who is highly allergic.

OAS can occur at anytime of the year. Although there is no definitive test for the syndrome, affected individuals often have a positive allergy skin test or blood test for specific pollen, along with a history of symptoms after ingestion of the suspected foods.

Different Reactions Based on Different Allergies


Cross-reactivity (not OAS) can occur between latex allergies and food items such as bananas, avocados, kiwi, chestnut and papaya.

Managing Your Symptoms
If you have symptoms of OAS, avoid eating these foods, especially during allergy season. If you have latex allergy, track foods that might be causing a cross-reaction.

Another way to reduce cross-reactions with food is to bake or microwave the food. Eating canned food may also limit the reaction. And, peeling the food before eating may be helpful, as the offending protein is often in the skin.


There are indications that in many patients OAS worsens during the pollen season of the pollen in question.

Video: What is an oral allergy syndrome? »

AAAAI - American Academy of Allergy Asthma & Immunology