Common Foods that Trigger Oral Allergy Syndrome

Bowl of sliced banana, orange, and apple

Verywell / Zorica Lakonic

Oral allergy syndrome (OAS) is a type of food allergy. People with OAS are sensitive to specific types of pollen as well as the foods related to those pollens. OAS is sometimes also called Pollen Food Allergy Syndrome.

What is Oral Allergy Syndrome?

Most people are familiar with common food allergies to things like peanuts, shellfish, tree nuts, etc. However, it is also possible to have less common allergies to things like citrus or celery.

In many cases, these reactions are caused by oral allergy syndrome (OAS). People with OAS have usually already been diagnosed with nasal allergies to things like tree, weed, or grass pollen.

Some foods contain proteins that are similar in structure to these inhaled allergens. This causes people with OAS to have food allergy symptoms when they consume those foods. This is a process known as cross-reactivity.

Cross-reactivity has been documented between birch pollen, mugwort pollen, grass pollens, ragweed, and Timothy grass with a variety of fruits, legumes, grains, nuts, seeds, vegetables, herbs, and spices.

A List of Foods That Can Trigger OAS

Here are some of the most common food triggers of OAS:

Apples

About 50% to 75% of people with an allergy to birch pollen and mugwort pollen also react to raw apple due to OAS.

Symptoms usually appear in the mouth and can occur within five minutes of eating an apple. For most people, the symptoms will occur within 30 minutes.

Symptoms tend to resolve when you stop eating the apple. It is also possible to have a more severe reaction, such as throat swelling. This can cause breathing difficulty.

Citrus

An allergy to citrus may happen when you eat one or more of the following fruits:

  • Orange
  • Grapefruit
  • Lemon
  • Lime

Reactions can range from an itchy mouth to full-fledged anaphylaxis. Anaphylaxis is a life-threatening allergic reaction.

There is cross-reactivity between different citrus fruits. This means allergy to one citrus fruit increases the likelihood of allergy to another. Some pollens that may cross-react with citrus due to their similar protein make-up include:

  • Grass pollens
  • Timothy grass
  • Birch pollen
  • Mugwort pollen

Bananas

Allergic reactions to banana vary widely and may include:

  • Itching of the mouth and throat
  • Hives (urticaria)
  • Swelling (angioedema)
  • Wheezing

Symptoms are most closely related to oral allergy syndrome and are localized in the mouth. In most cases, they begin within minutes of eating the fruit.

Cross-reactivity with ragweed is known to play a role in allergic reactions to bananas.

Spices

Coriander is in the family of spices that includes:

  • Caraway
  • Fennel
  • Celery

All of these spices have been associated with allergic reactions. Cinnamon, saffron, and mustard also have been noted for causing reactions.

Across the globe, spices have become some of the most common food allergens. Cross-reactivity is commonly due to:

  • Birch pollen
  • Mugwort pollen
  • Grass pollens
  • Timothy grass

The main symptom is itching in the mouth.

Some spices, including oregano, thyme, coriander, caraway seed, cumin, and cayenne pepper, have been associated with an anaphylactic reaction. This is extremely rare, however.

Celery

Celery allergies are relatively common. They may be due to cross-reactivity to birch pollen and mugwort pollen, as well as grass pollens and Timothy grass. According to some research, 30% to 40% of allergic individuals are sensitized to celery.

The most common symptoms of a celery allergy include itching and swelling in and around the mouth. Occasionally, there can be a whole body response, sometimes leading to anaphylaxis.

Coconut

Coconut allergy is very rare. The FDA classifies coconut as a tree nut for the purposes of ingredient labeling and consumer protection. Coconut is not a tree nut, however. Most people with a tree nut allergy can safely eat coconut.

Few people have a true coconut allergy, but they do exist. Symptoms include an itchy mouth and, extremely rarely, anaphylaxis. Products such as lotions and soaps containing coconut may cause contact dermatitis in some people.

Latex

Latex is produced from the sap of the rubber tree. The sap contains proteins that are similar to those found in other foods, especially fruit.

Between 30% and 50% of those with a natural rubber latex allergy are sensitized to these other foods. This is called latex-fruit syndrome. In people with this condition, eating these foods can cause allergy symptoms.

With latex-fruit syndrome, it's most common to see cross-reactivity with:

  • Avocado
  • Banana
  • Cassava
  • Chestnut
  • Kiwi
  • Mango
  • Papaya
  • Passion fruit
  • Tomato
  • Turnip
  • Zucchini
  • Bell pepper
  • Celery
  • Potato
  • Custard apple

Sensitivity to various other foods has been recorded as well.

If you are allergic to latex and have had a reaction to a food, you should avoid that food. If there is doubt, you may need to do an oral challenge test of the food under the supervision of a healthcare provider.

Symptoms of Oral Allergy Syndrome

Symptoms of OAS usually appear in the mouth. It is uncommon for them to appear elsewhere or to progress to anaphylaxis, though it can happen. Typically, symptoms include:

  • An itchy mouth
  • A scratchy feeling in the throat
  • Swelling of the mouth, lips or tongue

Symptoms of OAS usually disappear on their own and do not require treatment. This typically happens as soon as you stop eating the food.

People with OAS have a low risk of anaphylactic shock, but it can happen. Watch out for symptoms like trouble breathing, swollen throat, flushing, itchy skin, and anxiety or confusion. If any of these symptoms occur, seek medical care at once.

How is Oral Allergy Syndrome Diagnosed?

OAS can usually be diagnosed based on your symptoms and medical history. Your healthcare provider may also want to do a skin prick test or an oral food challenge.

A skin prick test involves introducing an allergen into a small prick on your skin. If you are allergic, you will develop a reaction at the site.

During an oral food challenge, you will eat the food in the presence of your healthcare provider, who will assess your symptoms and decide if the food might be dangerous for you.

Treatments for Oral Allergy Syndrome

Because it is possible for OAS to progress to a more severe allergic reaction, your healthcare provider will advise you to avoid eating foods that cause even a mild reaction. 

You may be able to eat these foods if they are cooked, but talk to your healthcare provider first. Either way, you will need to pay close attention to your symptoms. If you have an allergic reaction that spreads beyond your mouth, it could put you at risk for anaphylaxis. If this is the case, you may need to carry an EpiPen (epinephrine) in case you have a severe allergic reaction. 

Summary

Oral allergy syndrome is a reaction to proteins in foods that are similar to those found in certain pollens. If you are allergic to common pollens like grass, mugwort, birch, or ragweed, you may also develop mild food allergies.

OAS may cause allergic symptoms in your mouth when you eat things like citrus or bananas, legumes, nuts, seeds, and vegetables such as celery. Usually, these symptoms go away without treatment. If they progress beyond your mouth, however, they can put you at risk for anaphylaxis. Seek emergency care if you have swelling in your throat or trouble breathing after eating fruit or any other food.

A Word From Verywell

If you have a respiratory allergy to common pollens, you should be aware of the possibility of oral allergy syndrome.

Talk to your healthcare provider if you've ever experienced symptoms after eating one of these potentially cross-reactive foods.

Frequently Asked Questions

  • How is oral allergy syndrome diagnosed?

    Several tests may be used to diagnose OAS, including a skin prick test, a blood test, and an oral food challenge.

  • Is oral allergy syndrome treatable?

    Yes. The most effective way to treat a food allergy, including OAS, is by avoiding the trigger. Always read the ingredient list on foods that might contain the offending substance, and ask restaurant staff about it before ordering.

  • Will cooking foods remove allergens?

    Yes. High temperatures break down the proteins responsible for OAS. Other strategies are to eat the food in canned form or to peel foods that can be peeled. This is because the proteins responsible for allergies are often concentrated in the skin.

  • Can a food allergy suddenly occur?

    Yes. In fact, research has shown that food allergies are on the rise in both adults and children and that oral allergy syndrome is the most common form of adult-onset food allergy. People may develop allergies to foods they could previously eat without symptoms.

  • What foods can I safely consume if I have oral allergy syndrome?

    Unless you have known allergies to other foods, you should be able to consume anything other than the foods that cause an allergic reaction. With OAS, the important thing is to avoid those foods that cause symptoms.

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17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Joneja JV. The Health Professional’s Guide to Food Allergies and Intolerances.