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Oral allergy syndrome: A surprising allergic reaction

A woman selects an orange at a sidewalk fruit stand.

April 12, 2024—If your mouth or throat has ever become itchy after eating raw fruits or vegetables, you may suspect a food allergy. But those symptoms might actually be triggered by oral allergy syndrome (OAS).

OAS happens when seasonal pollen allergies spark a reaction to certain foods, including apples, bananas and bell peppers.

The food-plant connection

According to the American Academy of Allergy, Asthma & Immunology, people with OAS have reactions to different foods based on the type of seasonal allergies they have. That's because the proteins in certain fruits and vegetables are similar to those in some trees and grasses. And, sometimes, the immune system can be confused.

OAS, sometimes called pollen fruit syndrome or pollen food allergy syndrome, happens when your immune system responds to the food protein as if it were an allergen. This is called cross-reactivity.

For example, if you are allergic to birch trees, you may react when you eat pitted fruit, carrots or celery. If you have a ragweed allergy, you may notice symptoms when you eat melons or bananas.

Cooking or heating foods destroys the proteins that cause OAS. That makes cooking a great way to enjoy those foods without experiencing OAS symptoms.

OAS symptoms

When you eat a food that triggers OAS, you might experience symptoms such as:

  • Itching and tingling of the mouth, the throat and sometimes the lips.
  • Slight swelling and bumpiness of the mouth, throat or lips.
  • Redness, itching or mild swelling of the hands when handling OAS-causing raw fruits and vegetables.

In rare cases, a person can develop sudden, severe symptoms elsewhere in the body, such as hives, vomiting or difficulty breathing. This is called anaphylaxis, and it can be serious—even deadly.

OAS symptoms begin within a few minutes of eating the trigger food and disappear shortly after swallowing—your stomach acids easily destroy OAS-causing allergens.

When to seek medical attention

OAS is typically mild and doesn't require treatment. But other types of food allergy can be serious. If you're not sure which you're experiencing, talk to your doctor. You should also see a doctor if your symptoms:

  • Become progressively worse.
  • Are caused by eating cooked fruits and vegetables.
  • Are caused by eating nuts.
  • Give you significant throat discomfort.
  • Are severe and develop in other areas of your body besides your mouth and throat.

Your doctor or allergy specialist can determine if your reaction is OAS or a more serious food allergy. And if pollen allergies like the ones that cause OAS are affecting you, it may be time to consider long-term allergy treatment. Our interactive tool can help you decide if it's right for you.


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