Ask the allergist is a regular feature in our newsletters where Canadian allergists answer your questions! Please note, the allergists featured in this series answer questions on general topics, please talk to your doctor if you have questions about your own health or the health of your child.
This month we are revisiting a past feature on pollen food allergy syndrome, answered by Dr. Julia Upton.
1. What is pollen food allergy syndrome/oral allergy syndrome? Is it considered a food allergy or other condition?
Oral Allergy Syndrome (OAS), now usually called Pollen Food Allergy Syndrome (PFAS) 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 PFAS 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 PFAS who also have positive allergy tests to pollen – see below for the symptoms of PFAS. Usually there are positive skin prick tests to the fresh fruits or vegetables which cause symptoms.
2. What are the symptoms of PFAS? Can the symptoms lead to anaphylaxis?
The symptoms 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, PFAS 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, PFAS 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 PFAS, 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 PFAS avoid these foods?
Usually people with PFAS 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 PFAS 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 PFAS 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.
Learn more
This one-pager provides details on the foods that may trigger symptoms in people with allergies to various pollens.
This session will cover common triggers, diagnosis, strategies for symptom management, and advances in treatment. You will also get practical insights and evidence-based guidance on navigating this condition.
The webinar is on August 20, 2025 from 12pm-1pm EDT.
Dr. Julia Upton is on staff at the Hospital for Sick Children in the Immunology and Allergy Department; and an Associate Professor in the Department of Paediatrics at the University of Toronto. She is on the Board of Directors of the Canadian Society of Allergy and Clinical Immunology, and is 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.
Do you have a food allergy-related question you’d like to ask an allergist? If so, send it along to us at info@foodallergycanada.ca.
Tags: ask the allergist, OAS/PFAS, pollen food allergy syndrome