What Is Oral Allergy Syndrome and How Do You Treat It?


What is oral allergy syndrome (OAS)?

Oral allergy syndrome, also called pollen-food allergy syndrome, is an allergic reaction that can affect people that are allergic to certain types of pollen. The body's immune system can overreact to proteins found in fresh fruits, vegetables, or nuts and cause itching, swelling, or tingling in the mouth and throat.

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Oral allergy syndrome (OAS) is a cross-reactivity allergic reaction that can occur in people who have pollen allergies when they eat certain raw fruits or vegetables. This cross-reactivity happens because some foods contain proteins that are similar to the proteins in different types of pollen. Symptoms of OAS typically include itching or swelling around the lips, tongue, or throat. 

What Causes Oral Allergy Syndrome?

When someone has allergic rhinitis or an environmental allergy to pollen, their immune system has mistaken that pollen as a threat to the body. The immune system will raise the body’s defenses and release histamine to try to get rid of the allergen. The release of histamine is responsible for physical allergy symptoms that can affect your nose, eyes, throat, skin, stomach, lungs, and mouth. While pollen allergies typically cause symptoms like watery eyes, sneezing, and a runny nose, they can also be responsible for OAS.

When you are allergic to pollen from grasses, trees, or weeds, your body can mistake certain proteins in raw fruits and vegetables for the proteins in the pollen you are allergic to. When you eat a food that has similar proteins, your immune system can respond as if you have been exposed to pollen, resulting in an allergy reaction.

Common Triggers for Oral Allergy Syndrome

The specific foods that might trigger your OAS symptoms will vary based on what types of pollen you are allergic to. Visit our allergens blog to learn more about what foods to watch out for your specific pollen allergies. Some of the common triggers include:

  • pears and apples
  • tomatoes and avocados
  • tropical fruit (bananas, kiwi)
  • stone fruit (peaches, nectarines, apricots, cherries, plums)
  • melons (watermelon, cantaloupe, honeydew)
  • vegetables (peppers, carrots, celery, cucumber)
  • nuts (almonds, peanuts, hazelnuts, walnuts, chestnut)

What Allergies Cause Oral Allergy Syndrome?

Pollen allergies to grasses, trees, or weeds are what cause OAS. Birch pollen is a type of tree pollen that has a lot of foods it has cross-reactivity with. Another common allergen that causes OAS is ragweed pollen. Grass pollen also can cause OAS. Some common grass pollen allergies include allergies to Timothy, Bermuda, and rye grasses.


Food Cross-Reactive Pollen
Apples Birch
Cherries Birch, Alder
Peaches Birch, Alder
Pears Birch
Plums Birch, Alder
Strawberries Birch
Kiwi Grass
Peanuts Birch, Alder, Mugwort
Almonds Birch, Alder
Hazelnuts Birch
Walnuts Birch


Oral Allergy Syndrome and Pollen Cross-Reactivity

Oral allergy syndrome is a type of allergic reaction that occurs when the immune system mistakes proteins in certain raw fruits, vegetables, and nuts for pollens. OAS is often referred to as "pollen-food allergy syndrome" because it is triggered by proteins in certain foods that are similar to proteins found in pollen. People who are allergic to pollen from trees, grasses, or weeds are most likely to have OAS. The phenomenon of OAS is known as cross-reactivity, because the immune system reacts to proteins in the food as if they were pollen.

Oral Allergy Syndrome Pollen and Food Cross-Reactivity Chart

How Long Do Symptoms Last for OAS?

The symptoms of OAS often subside quickly. Oral allergy syndrome usually only lasts between 5 to 30 minutes. However, if you do have a more severe allergic reaction where you have trouble breathing, like anaphylaxis, you need to seek immediate emergency medical attention. If you experience severe nausea or vomiting you should also seek medical attention.

How to Avoid OAS?

There are several ways to decrease your OAS symptoms. If you know what foods cause your OAS symptoms you can limit your exposure to those foods or you can also try cooking any fresh fruits and vegetables. The heat changes the proteins in fruits and vegetables enough that typically your body then doesn't have as much of a reaction. You should not try this tip if you know you have a severe food allergy. If you have a severe allergy to a food, make sure to carry an epinephrine auto-injector to treat any potential severe reactions.

Diagnosis of Oral Allergy Syndrome

Allergy tests are great because they can show you what allergens you should avoid, including both indoor and outdoor allergens. To identify what allergens are causing your OAS symptoms and know what foods to look out for, it is important to get an allergy test to know exactly what you are allergic to. This makes it easier for you to treat symptoms and reduce your exposure. Several different allergy tests can be used to identify what allergens are triggering your symptoms.

Skin Prick Test

Prick testing has to be done at the doctor's office. This test involves using a needle tipped with different allergens and scraping your skin with each substance in the panel. After a short time, the doctor will look to see if the skin is red, itchy, or swollen in any of the spots that were pricked. This test requires you to make appointments, go in for the test, and deal with an uncomfortable and unpleasant testing experience.

At-Home Allergy Test

At-home allergy tests are convenient and an easy way to determine what you are allergic to. With Wyndly you can get an at-home allergy test shipped right to your home. Once your test arrives, all it takes is a small finger prick so we can test your blood sample and look for allergen-specific IgE. Once you return your test to our lab, your test will be processed and our doctors will interpret your results. You will then meet with one of our allergy doctors to go over your test results and get a personalized treatment plan based on your results and allergy history.

Treatment of Oral Allergy Syndrome

Treating your allergy symptoms using immunotherapy can often decrease your oral allergy syndrome symptoms. Sublingual immunotherapy introduces small doses of allergens to your immune system. This retrains your immune system to stop reacting to allergens when they’re in your environment. Sublingual immunotherapy is just as effective as allergy shots and can be taken from the comfort of your home.

Want Your Oral Allergy Syndrome to Go Away?

If you are looking for long-term relief from your allergy symptoms, Wyndly is the answer. Our doctors will create a personalized treatment plan based on your allergies and allergy history to get you lifelong allergy relief. Take our easy 2-minute online assessment now to get started!


 Most Common Season Spring Summer Fall
Types of pollen and foods that may cross-react Trees Grasses Weeds
Pitted fruit
Apple X
Apricot X
Cherry X
Peach X
Pear X
Plum X
Bell pepper

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