What is Oral Allergy Syndrome?

Also known as pollen fruit syndrome or pollen fruit allergy syndrome (PFAS), oral allergy syndrome is a cross-reactivity that occurs in patients with existing allergic rhinitis when they consume certain fruits and vegetables.

Since the proteins found in these fruits and vegetables are very like the ones found in certain pollens, patients with pollen-triggered rhinitis have a contact allergic reaction when eating these foods. As an example, as many as three out of four adults with an allergy to birch tree pollen will have a contact allergic reaction when consuming apples or celery.


The symptoms associated with OAS often appear as soon as the patient has eaten the fruit, affecting the face, mouth, lips, tongue, and throat. 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. While there is currently no definitive test for identifying the presence of OAS, patients with symptoms related to the disorder often have a positive diagnosis of a pollen allergy and have experienced regular symptoms when consuming certain fruits and vegetables.

Signs and Symptoms of Oral Allergy Syndrome

The signs and symptoms associated with oral allergy syndrome vary from one patient to the next. In general, the most common symptoms include:

  • Itchiness in the face and in the mouth
  • Swelling in the mouth, face, lips, tongue, and throat

Most oral allergy syndrome symptoms appear right after someone has consumed raw vegetables or fruits, but occasionally a patient will experience a delayed reaction and have symptoms hours later. Additional, less common symptoms can include irritation in the gums, eyes or nasal cavity. While symptoms of oral allergy syndrome can happen all year round due to the wide availability of out of season fruits and vegetables, symptoms are also worse during the spring and fall months when there is more pollen in the air.


Patients with OAS can be triggered by a single food source or from many different types of food. In some cases, patients will also only react to certain varieties; for example, someone might react to one type of red apple, but not to a type of green apple.

In general, a patient’s triggers correlate with whatever type of seasonal allergy they have.

  • Those with ragweed allergies 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, and more
  • 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 Oral Allergy Syndrome is Diagnosed?

As with diagnosing any condition, diagnosing oral allergy syndrome involves multiple steps. Diagnosing the condition can be challenging given the multiple factors involved. A doctor will likely begin with a physical exam and medical history.

When taking the medical history, the doctor will ask after a family history of allergies as well as if the patient has any diagnosed allergies. A doctor or allergist may also recommend testing. Testing options for oral allergy syndrome can include both skin tests and blood tests to confirm a diagnosis. The presence of a confirmed test for a pollen allergy can, of course, help in the diagnostic process.

oral allergy family

Oral Allergy Syndrome Treatment Options

As with all allergies, the best way to treat oral allergy syndrome is to avoid exposure to the foods or vegetables associated with a patient’s particular diagnosis. Oral allergy syndrome treatment can also include OTC and prescribed antihistamines or immunotherapy. There are also some natural remedies when it comes to how to treat oral allergy syndrome. Oral allergy syndrome natural treatment options include peeling a fruit to avoid concentrated proteins, cooking fruits and vegetables, and eating canned fruits and vegetables during spring and fall.


The main risk factor for oral allergy syndrome is the presence of a pre-existing pollen 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?

Is Oral Allergy Syndrome Dangerous?

Can Oral Allergy Syndrome Cause Hives?

How Long Does Oral Allergy Syndrome Last?

How Common Is Oral Allergy Syndrome?