Oral allergy syndrome (OAS) affects up to 70% of people who have pollen allergies. It can start with young children and increase with age.

*According to Stanford Healthcare.

What is oral allergy syndrome (OAS)?

Also known as “pollen-food allergy syndrome”, pollen fruit or pollen fruit allergy syndrome (PFAS), oral allergy syndrome occurs in patients with existing allergic rhinitis (hay fever) due to cross-reactivity between proteins in certain fresh fruits, vegetables, and nuts, and pollen from trees, grasses, and weeds.

It’s important to note that cooking or processing the offending fruits, vegetables, or nuts may break down the allergenic proteins and reduce or eliminate the symptoms of OAS.

What causes oral allergy syndrome (OAS)?

Oral Allergy Syndrome is a problem all over the world, and it may be the most common food allergy since it is based on pollen allergies which are much more prevalent and can occur at any age.

For example, as many as three out of four adults with an allergy to birch tree pollen will have a localized oral reaction when consuming apples or celery. OAS is considered a mild allergy, but on rare occasions it can cause more serious reactions.

Unlike pollen allergies, OAS can occur at any time of year, given the fact that many fruits and vegetables are sold out of season in the modern world. Symptoms are worse during the spring and fall months when there is more pollen in the air.

Symptoms of oral allergy syndrome (OAS)

Most OAS symptoms appear right after someone has consumed raw vegetables or fruits, but rarely you can experience a delayed reaction and have symptoms hours later.

Symptoms usually only last a few minutes after eating the food causing the reaction. Rarely, (approximately 9% of the time) you may experience a more serious allergic reaction and about two percent of people with symptoms will experience anaphylaxis or difficulty breathing.

The most common symptoms of OAS include:

  • Itching or swelling of the lips, mouth, throat, and tongue
  • Redness and irritation of the mouth or throat
  • Dryness or a metallic taste in the mouth
Woman farmer picking ripe peaches from a tree and placing them into basket in the garden

Common triggers of oral allergy syndrome (OAS)

Patients with OAS can be triggered by a single food source or from many different types of fruits, vegetables and nuts.

Some individuals may only show allergy to only one particular food, and others may show an allergic response to many foods.

In other cases, patients will also only react to certain varieties; for example, someone might react to one type of raw apple, but not to another type of apple.

Reactions may begin with one type of food and others will develop later. You may suddenly develop OAS to something you have enjoyed eating your entire life.

Existing allergies to weed pollen and tree pollen can be indicators of existing or future allergic reactions to raw foods. In general, a patient’s triggers correlate with whatever type of seasonal allergy they have.

  • Those with ragweed allergies can react to: bananas, melons, zucchini, cucumber, dandelions, and chamomile.
  • Those with birch allergies react to: apples, peaches, pears, cherries, apricots, plums, prunes, nectarines, kiwi, carrots, celery, potatoes, peppers, coriander, hazelnuts.
  • Those with grass allergies react to: peaches, celery, tomatoes, oranges, and melons.
  • Those with mugwort allergies react to: apples, celery, kiwi, peanuts, fennel, carrots, parsley, sunflower seeds, peppers, and coriander.
  • Those with alder allergies react to: pears, apples, celery, almonds, hazelnuts, cherries, peaches, and parsley.
  • Finally, those with a latex allergy may react to: avocados, kiwis, bananas, chestnuts, and papaya.

How is oral allergy syndrome (OAS) diagnosed?

A lot of the tests used to diagnose OAS are the same ones used to diagnose pollen allergies. Oral allergy syndrome is like any other condition in that it takes more than one step to figure out what’s wrong. 

Most likely, your doctor will start with a physical exam and a review of your health history. When taking a medical history, the doctor will ask about allergies in the patient’s family and if the patient has any allergies that have been diagnosed. 

To figure out which foods are causing your allergies, your doctor may suggest an elimination diet in which you avoid the foods that are making your mouth itch or giving you a lot of throat pain. 

A doctor or an allergist who has been certified by the board may also suggest testing. To confirm a diagnosis of oral allergy syndrome, doctors can use both skin tests and blood tests. They can test for pollen and food allergies, but food allergy testing is often negative in oral allergy syndrome.

When should you see a doctor about oral allergy syndrome (OAS)?

You should see a board-certified allergist if you develop symptoms that are severe, for example:

  • Your throat is very sore
  • You have difficulty swallowing
  • You have trouble breathing
  • Nuts are causing your symptoms
  • Symptoms after eating cooked fruits and vegetables
Children and mother preparing fruits and vegetables to avoid oral allergy syndrome symptoms naturally.

Oral allergy syndrome (OAS) treatment options

As with other allergies, the best way to treat oral allergy syndrome is to stay away from the foods or vegetables that a patient is allergic to. Because of this, your allergist will probably tell you to stop eating the food that is making your symptoms worse. 

Beyond that, your doctor may recommend an over-the-counter antihistamine like Zyrtec, Benadryl or Allegra to relieve the itching or mouth tingling.

An EpiPen may be prescribed for more severe reactions. Immunotherapy may be recommended as a long-term solution for pollen allergies which can sometimes improve oral allergy syndrome.

Oral allergy syndrome (OAS) home remedies

While there are no cures for oral allergy syndrome (OAS), you can minimize your allergic reaction to fresh fruits and vegetables with the following natural treatment options:

  • Cooking or processing: This breaks down the allergenic proteins in the offending fruits, vegetables, or nuts and reduces or eliminates the symptoms of OAS.
  • Avoidance: The best way to prevent OAS symptoms is to avoid the foods that trigger them.
  • Eating canned or frozen fruits and vegetables: This is a safe option for avoiding OAS symptoms since the proteins that react to the pollens in fresh food are broken down during processing.
  • Peeling the fruit or vegetable: This helps you avoid concentrated pollen proteins.

Risk factors for oral allergy syndrome (OAS)

The main risk factor for an allergic reaction to fresh fruits and vegetables or oral allergy syndrome is the presence of a pre-existing pollen allergy or latex allergy.

Research has shown that patients with OAS may have some additional risk factors beyond atopy, though research in this area is ongoing. It is known that cases of OAS appear more frequently in women than in men.

Pre-existing pollen allergy

Pre-existing latex allergy


Frequently Asked Questions

Is oral allergy syndrome curable?

Are allergic reactions to raw fruit and vegetables dangerous?

Can oral allergy syndrome cause hives?

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How common Is oral allergy syndrome?