Oral allergy syndrome (OAS) is a common food-related allergy that develops in adults. OAS is connected to environmental allergies, such as hay fever. When a person has oral allergy syndrome, certain fresh fruits, nuts, and vegetables that contain traces of pollen trigger reactions in the mouth. For this reason, the condition is sometimes called pollen-fruit allergy syndrome. The symptoms tend to be worse during times of the year when pollen is heavy in the air.

Different people are triggered by different foods, but OAS only happens as the result of a pollen-based trigger. Some common triggers of OAS include:

  • bananas
  • cherries
  • oranges
  • apples
  • peaches
  • tomatoes
  • cucumbers
  • zucchinis
  • bell peppers
  • sunflower seeds
  • carrots
  • fresh herbs, such as parsley or cilantro

Tree nuts, such as hazelnuts and almonds, can cause an allergic reaction in people who have OAS. Oral allergy syndrome is different from other nut allergies, though, which can prove fatal. People with oral allergy syndrome generally won’t have a severe allergic reaction. Also, the reaction will be confined to the area of the mouth.

The symptoms of OAS can vary, but they tend to be concentrated in the area of the mouth. They rarely affect other areas of the body. When your oral allergy syndrome is triggered, you may have these symptoms:

  • an itching or tingling on your tongue or the roof of your mouth
  • swollen or numb lips
  • a scratchy throat
  • sneezing and nasal congestion

The best treatment for oral allergy syndrome is straightforward: Avoid your trigger foods.

Some other easy ways to reduce OAS symptoms include these tips:

  • Cook or heat your food. Preparing food with heat changes the chemical composition, and many times eliminates the allergen.
  • Buy canned versions of a vegetable or fruit.
  • Peel the skin off vegetables or fruit. The offending protein is often found in the skin of the produce.

Over-the-counter treatments

Over-the-counter histamine blockers, or antihistamines, used for hay fever may work for oral allergy syndrome symptoms, according to a paper published in Allergy. Diphenhydramine (Benadryl) and fexofenadine (Allegra) can be used to relieve the itching, watery eyes, and scratchy throat that come during high-pollen days for people with allergies. They can sometimes suppress OAS reactions as well.


People that were treated with immunotherapy for OAS have had mixed reactions. In one clinical study, subjects could tolerate small amounts of the birch pollen triggers after immunotherapy, but they couldn’t overcome OAS symptoms completely.

Because the symptoms of OAS are not dangerous, ask your general health practitioner if you can experiment once in a while and see what you react to.

People who have allergies to birch pollen, grass pollen, and ragweed pollen are most likely to have oral allergy syndrome, according to the American College of Allergy, Asthma, and Immunology.

Young children are not usually affected by OAS. Often, young adults will have symptoms of OAS for the first time after having eaten trigger foods for years without a problem.

The pollination season of April, May, and June tend to be the peak months for oral allergy syndrome. Sometimes September and October will bring on symptoms again as leaves fall from the trees and seeds are heavy in the air.

In 9 percent of people with oral allergy syndrome, symptoms can become more severe and require medical intervention. If you have a reaction to a pollen-based food that extends beyond the area of your mouth, you should seek medical attention.

In some very rare cases, OAS can trigger anaphylaxis. In other cases, people confuse their serious nut or legume allergies with oral allergy syndrome. Make sure you speak to your doctor about the intensity and severity of your symptoms. You might need to be referred to an allergist to be certain that your symptoms are caused by oral allergy syndrome.