HomeAsk the allergist: Your questions answered – September 2019

Ask the allergist: Your questions answered – September 2019

September 13, 2019

Ask the allergist is a regular feature in our newsletters where Dr. Julia Upton answers your questions!

Dr. Upton
Dr. Julia Upton

Dr. Julia Upton is a Canadian allergist who is on staff at Toronto’s SickKids Hospital in the Immunology and Allergy Department. She is an Assistant Professor in the Department of Paediatrics at the University of Toronto and is the Section Chair of Food Allergy and Anaphylaxis with the CSACI. Dr. Upton is also a member of our Healthcare Advisory Board.

Please note: Dr. Upton is answering as an individual allergist and her answers do not constitute an official position of her affiliated organizations. Her responses are for informational purposes only and do not constitute specific medical advice, recommendations, diagnosis, or treatment. Please talk to your doctor about any concerns or questions you may have regarding your own health or the health of your child.

This month she answers your questions about Oral Allergy Syndrome/Pollen-Food Syndrome.


1. What is Oral Allergy Syndrome or Pollen-Food Syndrome? Is it considered a food allergy or other condition?

Oral Allergy Syndrome (OAS), now usually called Pollen-Food Syndrome (PFS) is considered a type of food allergy in which allergic symptoms can result from the proteins in certain fresh fruits or vegetables, and/or nuts which have a structure similar to those in pollen. People with PFS are allergic to pollen. Sometimes the pollen allergy is mild and the person is not aware of it.

The diagnosis is made in people with symptoms of PFS who also have positive allergy tests to pollen – see below for the symptoms of PFS. Usually there are positive skin prick tests to the fresh fruits or vegetables which cause symptoms.

2. What are the symptoms of OAS/PFS? Can the symptoms lead to anaphylaxis?

Healthy food selection. Shopping bag full of fresh vegetables and fruits. Flat lay food on table

The symptoms of OAS/PFS are usually itchiness of the mouth and throat when eating fresh fruits or vegetables and/or nuts related to the pollen to which you are allergic. An example of some of the fruits, vegetables and nuts can be found here. This list is not meant as a list of all the foods to avoid, but rather a list of foods which are known to cause symptoms. Most people have symptoms to only a few pollen-related foods.

Although it is uncommon, OAS/PFS can lead to anaphylaxis. There are some factors that may make an anaphylactic reaction more likely such as, the symptoms experienced, which food causes the symptoms, and testing results. The chances of anaphylaxis are greater if you’ve had a previous allergic reaction to the fruits or vegetables which was more than mouth itch, if you have symptoms to the cooked food, and/or positive skin prick tests to commercial allergy extract. Also, OAS/PFS to nuts is a higher risk for progression to anaphylaxis.

There are also factors which increase the chances for a more severe reaction in general, such as eating a larger amount of the food, exercising after eating a particular food, being sick or feverish, or taking non-steroidal anti-inflammatory medications (such as ibuprofen).

Therefore, in cases where you have had symptoms more than a mild itch of the mouth/throat, symptoms to nuts, or particular patterns of allergy testing, your allergist may recommend that you avoid certain food and carry an epinephrine auto-injector.

3. When someone has OAS/PFS, will accidental exposure or an increase in exposure to allergens make future reactions more severe?

Exposure is not currently a known factor related to severity. Many people notice more severe symptoms during pollen season.

4. Should individuals with OAS/PFS avoid these foods?

Usually people with PFS avoid the fresh or raw version of the foods which cause them symptoms. They usually tolerate the food if it is well cooked or canned. Some people find they have less symptoms to peeled fruit. The symptoms can be very specific to certain types of fruits and vegetables. For example, it is possible to have symptoms to one type of apple and not to another. 

5. I have been recently diagnosed with OAS/PFS and I’m pregnant. How do I get the nutrients necessary for me and my baby while avoiding so many foods?

I would recommend that you discuss how to manage the foods you need to avoid with your physician and a dietitian. In general, most people with OAS/PFS react to a small number of foods and that’s what they should avoid, rather than every known food which might cause it. The avoidances of food can be tailored to your symptoms.


Thank you, Dr. Upton, for your insightful and helpful answers!


Do you have a question you’d like to ask Dr. Upton in the months to come? If so, please send it along to us at info@foodallergycanada.ca.

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