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Oral Allergy Syndrome

Oral Allergy Syndrome

Oral allergy syndrome - birch pollen

Do apples all of a sudden make your mouth itchy? You’ve been eating them for 15 odd years, and now this? If you are like me, you may have oral allergy syndrome.

It felt like every year, one or two new foods were causing what I thought at the time were allergic reactions that could lead to anaphylaxis. So every year, my food allergy list got longer. I did not know that I had developed oral allergy syndrome (OAS), better known as food pollen allergy syndrome. 

What is food oral allergy syndrome?

OAS can be pretty confusing at the start because the foods you are reacting to may feel random. To better understand OAS, consider the term itself, which is no longer preferred. Doctors now prefer the term food pollen allergy syndrome because symptoms do not have to be limited to the mouth. 

Oral allergy syndrome was the original term because the allergy symptoms experienced are primarily in your oral cavity, such as itching, scratchy throat, itchy mouth or lips, swollen lips, tongue, or throat. 

Pollen food allergy syndrome is now preferred because it better explains what is going on. As the food allergy symptoms occur due to the cross-reaction of pollen you are allergic to. So you start out with a pollen allergy and then develop sensitivity to certain foods related to the pollen. 

From here on out, we will now use pollen food allergy syndrome instead of oral allergy syndrome.

How do you know it is pollen food allergy syndrome?

The kicker is that some foods people experience pollen food allergy syndrome to are also common food allergens, such as tree nuts. So how do you know if you have a true allergy to something or are experiencing pollen cross-reactivity?

We talk about pollen food allergy syndrome and cross-reactivity on The Itch Podcast with Dr. G and Dr. Wright, a board-certified allergist and Medical Director at Thermo Fisher Scientific. Get all the information plus more on the episode!

Also on🎙 Spotify  🎙 Stitcher

Pollen food allergy syndrome and cross-reactivity

To better understand pollen food allergy syndrome, you need to understand what it means to have a cross-reactive allergy. 

Cross-reactivity occurs when your body’s immune system identifies the proteins in one substance (e.g. pollen) and the proteins in another (e.g. fruit & vegetables) as being similar.

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In pollen food allergy syndrome, your body recognizes a protein in the food as something similar to the pollen protein, which accounts for oral symptoms such as itching. 


Diagnosing pollen food allergy syndrome

Diagnosing pollen food allergy syndrome can be easy or complicated. I realized I had it because I could eat carrot cake or apple sauce but not eat carrot sticks or apple slices. Being able to eat the food cooked but not raw is your first tell. I also have a history of pollen allergies. 

For individuals with multiple food allergies and are unsure if it is pollen food allergy syndrome or a true allergy, your allergist can figure out what is happening by taking a detailed history and conducting allergy tests. 

Allergy tests for pollen food allergy syndrome

When you have an allergy, your body reacts to a protein in the food or plant and releases histamines causing the allergic response. Foods contain multiple proteins. Some of the proteins are minor, and some are major. 

Kortney's skin prick test
Kortney’s skin prick test for environmental allergies – she is very allergic to birch pollen

Skin prick & IgE blood test

When you do a skin prick test or an IgE blood test, there is no way to tell which proteins you are reacting to within the food. This means you test positive for a particular food, but it may not be to a major protein which is what would cause an allergic reaction that could be anaphylactic. 

Component testing 

If you eat a food, only get an itchy mouth, and have a positive IgE blood test, your doctor will consider doing another test called component testing. This will help determine if it is pollen food allergy syndrome. 

Component testing is a blood test that can help determine what proteins you are reacting to in that food. Through component testing, you break down the food into individual proteins and see which proteins you have IgE antibodies to. 

If you are IgE positive to minor proteins, the ones present in the tree or plant, you are unlikely to have an anaphylactic reaction. As you are allergic to a similar protein in pollen, your body will release histamine, giving you the oral symptoms.

 If you are positive to the major protein in the food itself, you are likely to have an allergic reaction.

See Also
Confidence with food allergies

Note that component testing is not yet available for all foods.

Oral challenge

If it looks like you are positive to only the minor protein, your allergist may tell you to go ahead and eat the food, or you may be able to do an oral challenge. 

You can see how I could eat almonds after this testing journey with my allergist a few years ago or check out this video 👇

You can still, for the most part, eat your pollen food allergy syndrome foods. Dr. Wright and Dr. G share some ways to lessen your symptoms on our episode of The Itch Podcast, available to listen now! 

Personally, after having one too many anaphylactic reactions, I avoid eating any foods that give me pollen food allergy syndrome. That is my personal experience. However, I know quite a few people who still eat these foods despite the symptoms.

If you are unsure if this is what is going on when you eat 🍎apples 🍑peaches 🍐 pears 🌰 hazelnuts, and the list goes on, it is best to head to your allergist to figure out what is happening. The journey to testing is worth the freedom you get from learning what you are reacting to. Trust me, knowing that the symptoms I get when eating almonds are because of a minor protein (i.e. pollen food allergy syndrome) has given me one less thing to worry about. 

This article was reviewed by Dr. Payel Gupta. 

Listen to The Itch Podcast episode about cross-reactive allergens:


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This article is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice. Always seek the guidance of your doctor or other qualified health professional with any questions regarding your health or a medical condition.


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