September 19, 2022

Pollen Food Syndrome: The Surprising Link to Allergies

Oral allergy syndrome (also called pollen food allergy syndrome) is a cross-reaction of allergens in food and pollens.

Raw fruits, vegetables and nuts contain proteins that are similar to the proteins in different types of pollen, including alder, birch, grass, mugwort and ragweed pollens. Eating these foods may cause uncomfortable symptoms, such as an itchy mouth, lips or throat.

Find out how to get a pollen food syndrome diagnosis and how to avoid and treat uncomfortable symptoms.

Oral Allergy Symptoms

The most common symptoms of oral allergy syndrome (OAS) may include:

  • Itching, burning or tingling of the mouth, tongue or throat
  • Swelling of the lips and tongue
  • Inflammation

Symptoms may vary in severity from person to person. While one person may experience minimal symptoms that disappear after the food is swallowed, some may experience discomfort for an extended period of time.

In some severe cases, OAS may cause throat swelling that may make it difficult to breathe or swallow. While anaphylaxis is uncommon, OAS may cause this reaction.

While pollen allergy symptoms are seasonal, OAS is perennial and symptoms may arise any time of year.

What’s the difference between OAS and food allergies?

A food allergy is when your immune system reacts to a food allergen, such as milk, eggs, peanuts, tree nuts, soy, wheat, fish or shellfish.

With oral allergy syndrome, you’re not allergic to the food itself; your body has a reaction to the cross-reacting proteins in both the food and the seasonal allergen.

Eating foods you’re allergic to may trigger more serious symptoms, such as rash, nausea, gastrointestinal issues, itching, shortness of breath, respiratory inflammation or anaphylaxis.

Symptoms with OAS are often less severe than food allergy symptoms and often dissipate after the food is swallowed. Some patients experience discomfort in the digestive tract after the food is swallowed, and about 9% of patients experience more severe symptoms. 2% of patients experience anaphylaxis.

Which allergens may trigger Oral Allergy Syndrome?

Not everyone who suffers from pollen-induced rhinoconjunctivitis has oral allergy syndrome. According to the Allergy and Asthma Network, only one out of three seasonal allergy sufferers have OAS.

The most common pollens associated with OAS include alder, birch alder, grass, mugwort and ragweed pollens.

Alder Pollen

One of the most common offenders of seasonal allergies is alder pollen. If you suffer from an alder pollen allergy and OAS, you may experience uncomfortable symptoms when eating the following foods:

  • Almonds
  • Apples
  • Celery
  • Cherries
  • Hazelnuts
  • Peaches
  • Pears
  • Parsley


Birch is another common seasonal allergen. The majority of people who suffer from OAS are allergic to birch.

The most common foods that contain cross-reacting proteins with birch alder include:

  • Almonds
  • Apples
  • Apricots
  • Avocados
  • Bananas
  • Carrots
  • Celery
  • Cherries
  • Chicory
  • Coriander
  • Fennel
  • Fig
  • Hazelnuts
  • Kiwi
  • Nectarines
  • Parsley
  • Parsnips
  • Peaches
  • Pears
  • Peppers
  • Plums
  • Potatoes
  • Prunes
  • Soy
  • Strawberries
  • Wheat

Sometimes people with birch allergies also show symptoms of OAS when eating peanuts.

Grass Pollen

Grass pollen is another common seasonal allergen. If you’re allergic to grass pollen and suffer from OAS, you may experience symptoms when eating the following foods:

  • Figs
  • Melons
  • Tomatoes
  • Oranges

Mugwort Pollen

Mugwort pollen season arises in late spring and early fall in much of the world (though in some areas of the U.S., mugwort pollen season happens from February to May).

If you’re allergic to this airborne allergen and you have OAS, you may experience symptoms when eating the following foods:

  • Carrots
  • Celery
  • Coriander
  • Peppers
  • Fennel
  • Parsley
  • Sunflower

Ragweed Pollen

Another common seasonal allergen is ragweed pollen. According to the Asthma and Allergy Foundation of America, 15% of Americans suffer from ragweed allergy symptoms in late summer and early fall.

If you suffer from ragweed pollen allergies and have OAS, you may also experience symptoms when eating the following foods:

  • Artichoke
  • Banana
  • Cantaloupe
  • Chamomile Tea
  • Cucumber
  • Dandelions
  • Echinacea
  • Hibiscus
  • Honeydew
  • Watermelon
  • Zucchini

It’s important to note that you may not experience OAS symptoms with all foods in each pollen cross-reactivity list above; you may only experience symptoms with one or several of the foods in these lists.  

If you’re allergic to any of the above pollens, you may not experience OAS symptoms at all.

Diagnosing OAS

Self-diagnosing oral allergy syndrome isn’t recommended, as self-misdiagnosis is common.

Oral allergy syndrome shares symptoms with other medical conditions; one common cause of similar symptoms may be pesticides or other food contaminants. There’s also a chance you may be experiencing a food allergy.

If you haven’t been previously diagnosed with allergies, there are two types of testing available: blood and skin scratch. You may also need to fill out a questionnaire or explain your symptoms to a clinician.

Skin scratch tests are performed in a clinician’s office and test for several different allergies at once. Blood draws are performed at a testing lab or at home.

Curex’s at-home allergy testing kit tests for 36 of the most common indoor and outdoor allergies. Order an at-home test kit, follow the instructions and send your sample to the lab. Results are usually available within a few weeks.

Curex also now offers a concierge test, too. A medical assistant will travel to your home or office and perform a blood draw to test for some of the most common indoor and outdoor allergies.

This is ideal for anyone who doesn’t want to travel to a lab or feels uncomfortable self-testing.

Treating Oral Allergy Syndrome

There is no cure for oral allergy syndrome. Medical professionals recommend avoiding trigger foods, cooking or processing food to break down the cross-reacting proteins (if this eases symptoms) and treating symptoms with allergy medications.

In some cases (though rare), patients may want to carry an EpiPen in case of anaphylaxis.

Food Avoidance

If you experience uncomfortable symptoms when eating certain fruits, vegetables and nuts, you may simply want to avoid these foods.

Once you’ve been tested for allergies, you’ll have a better understanding of which cross-reacting proteins are causing symptoms. Yet, not all patients experience symptoms with every fruit, vegetable or nut that contains cross-reacting proteins.

Someone with a grass pollen allergy may experience symptoms when eating figs but not melons, tomatoes or oranges.

If you know which foods cause symptoms, you may simply want to avoid those foods. Your doctor may also recommend treating symptoms with allergy medication or carrying an EpiPen in case of anaphylaxis.

Cooking Food

Cooking or processing food may help break down the cross-reacting proteins associated with oral allergy syndrome.

Many patients find that they can tolerate fruits, vegetables and nuts that have been cooked, canned, marinated in acids (such as vinegar or lemon juice) or otherwise processed to the point that the proteins break down.

Allergy Medications

Allergy medications have been proven effective in treating symptoms of OAS. Antihistamines may help reduce swelling and itching and other symptoms of pollen food syndrome.

If you suffer from severe symptoms, your doctor may recommend carrying an EpiPen in case of anaphylaxis.

Allergy Immunotherapy

Some studies suggest that allergy immunotherapy may help prevent symptoms of OAS.

Allergies are triggered when allergens enter the body; the immune system (which sees allergens as a potential threat) releases histamine to fight off the allergen. This histamine release is what causes uncomfortable symptoms.

When foods containing cross-reacting allergen proteins enter the body, the immune system views these proteins as a threat.

Allergy immunotherapy introduces small amounts of an allergen to the system. Over time, the immune system may stop recognizing allergens as a threat and stop responding by releasing histamine (or at least by releasing less histamine).

A 2008 study showed, “After 12 months, OAS was rated as much or very much improved in 72.9% of patients. Sublingual immunotherapy significantly reduced rhinoconjunctivitis symptoms and medication use.”

Subcutaneous Immunotherapy

Subcutaneous immunotherapy is more often prescribed in the U.S. than sublingual immunotherapy.

Otherwise known as allergy shots, subcutaneous immunotherapy introduces small amounts of allergens to the system via injection. This treatment is often administered in a doctor’s office weekly during the build-up phase and then monthly during the maintenance phase.

Sublingual Immunotherapy

Similar to subcutaneous immunotherapy, sublingual immunotherapy also introduces small amounts of an allergen to the system — except instead of by way of injection, sublingual immunotherapy is administered orally, underneath the tongue.

You may self-administer sublingual immunotherapy at home without clinician supervision (though you may need to make an in-person or telehealth appointment before your first dose).

Take our free quiz or contact a Curex Care Manager to see if at-home immunotherapy is right for you.

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