Mother watching girl eating orange

What is Oral Allergy Syndrome (OAS)?

Published date field Last Updated:

Has your mouth ever started itching after you take a bite out of a raw apple or banana? If you experience hay fever or nasal allergies, this allergic reaction may be due to oral allergy syndrome (OAS.) Though often considered a mild allergy, OAS occurs when the immune system confuses proteins in some foods with allergy-triggering proteins from pollen. Explore causes of OAS and the simple steps you can take to curb symptoms—so you can keep eating your favorite foods.

What Is Oral Allergy Syndrome?

Oral allergy syndrome is an allergic reaction in the mouth or throat caused by certain raw fruits, vegetables, or nuts. The immune system will trigger an allergic response when it can't differentiate between similar proteins found in foods and pollens. OAS is more likely to develop in teens and young adults who experience hay fever related to birch, ragweed, and grass pollens which have similar proteins to certain foods, according to Mayo Clinic.

What Causes Oral Allergy Syndrome?

OAS can occur any time of year with an increased chance of symptoms when seasonal allergies are more active. Oral allergy syndrome is caused by the cross-reactivity of airborne allergens found in certain raw foods. Common trigger foods of OAS include:

Fruit

  • Apples
  • Bananas
  • Cherries
  • Chestnut
  • Kiwi
  • Melon
  • Peaches
  • Peanuts
  • Plums
  • Tomatoes

Vegetables

  • Carrots
  • Celery
  • Cucumber
  • Parsnips
  • Potatoes
  • Zucchini

Nuts

  • Almonds
  • Chestnuts
  • Hazelnuts
  • Peanuts
  • Walnuts

Oral Allergy Syndrome Symptoms

Symptoms of OAS are relatively mild and generally only occur in the mouth about an hour after exposure to a food. Though uncommon, severe signs of oral allergy syndrome may involve difficulty breathing or swallowing. Contact a doctor or allergist if you experience food allergy symptoms after eating. Typical signs of OAS include itchiness or swelling in the following areas:

  • Mouth
  • Throat
  • Lips
  • Tongue
  • Face

How to Treat Oral Allergy Syndrome

Oral allergy syndrome treatment varies depending on the trigger and severity of the allergic reaction. Suppose you aren't able to identify the allergy trigger. In that case, a medical professional or allergist can help determine what's causing the allergic response and what kind of treatment is needed. They may recommend eliminating exposure to the allergy trigger if it's a mild case. Allergen immune therapy (pollen shots as a treatment for hay fever) and over-the-counter histamine blockers may also help resolve OAS symptoms.

The allergy-inducing proteins are commonly found in the skin of the food, so removing the skin can sometimes eliminate the allergy trigger. Fortunately, the proteins that cause OAS can easily break down if the food isn't consumed raw. Some methods for breaking down allergy-triggering proteins in food are:

  • Cooking or heating food with a stove, oven, or microwave.
  • Eating frozen or processed foods like applesauce.
  • Peeling off the skin.
  • Purchasing canned fruits or vegetables.
  • Avoid allergy-inducing foods that are dried or in dehydrated form.

Though oral allergy syndrome will likely cause only minor symptoms, visiting a medical professional is the best way to determine the proper treatment for you. Remember that just because you haven't previously had an allergic reaction to a particular raw food doesn't mean OAS can't appear later in life. Talk with your doctor if you think you are experiencing OAS!

paper airplane

Want more tips and offers sent directly to your inbox?

Sign up now

This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.

Mobile Top Image

Was this article helpful?

Thank you for submitting your feedback!

If you’d like a response, Contact Us.

Mobile Bottom Image