Oral Allergy Syndrome: Symptoms & Signs

Oral allergy syndrome (OAS), also known as Pollen Food Allergy Syndrome (PFAS), is a (usually) mild allergic reaction that is triggered by certain raw fruits or vegetables. As the name suggests, OAS is confined to the lips, mouth, and throat, and it typically first presents in older children, teens, and young adults—especially those who suffer from asthma or hay fever (or allergic rhinitis)—who have been eating the fresh fruits and vegetables in question for years without any issues.

What causes oral allergy syndrome?

OAS is caused by a cross-reactivity between plant proteins from pollen and fruits or vegetables. Cross-reactivity occurs when the proteins in one substance (in this case, pollen) are similar to the proteins found in another substance (fruits/vegetables), so the immune system sees them as the same and responds similarly to both.

People affected by OAS can usually eat the same fruits or vegetables in cooked form, since the heating process distorts the proteins, and the immune system no longer recognizes the food and produces a response. OAS often worsens during the pollen season of the pollen to which a person is allergic.

What are the symptoms of OAS?

Itchy mouth, scratchy throat, and/or swelling of the lips, mouth, tongue, and throat are the most common symptoms of oral allergy syndrome, though itchy ears and hives on the mouth are sometimes reported. The symptoms are usually confined to one area and do not normally progress beyond the mouth, though it is possible. Additionally, anaphylaxis from OAS is rare, however, it has been reported in a very small percentage of patients.

What are the common trigger foods for OAS?

While not everyone with a pollen allergy experiences oral allergy syndrome, people with birch, ragweed, or grass pollen allergies are most likely to develop OAS, and there are several foods that commonly trigger a reaction.

  • People with an allergy to birch pollenoften experience oral allergy syndrome when consuming:
    • Apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, and plum.
  • People withan allergy to grass pollen often experience oral allergy syndrome when consuming:
    • Celery, melon, orange, peach, and tomato.
  • People with an allergy to ragweed pollen often experience oral allergy syndrome when consuming:
    • Banana, cucumber, melon (i.e., watermelon, cantaloupe, and honeydew), sunflower seed, and zucchini.

What to do if you think your child has developed oral allergy syndrome?

Oral allergy syndrome is very rare in babies and toddlers under the age of 3, since children don’t typically develop hay fever, or seasonal allergies, until after the age of 3—and someone who develops oral allergy syndrome will always have pollen allergies first.

If you suspect your child has developed oral allergy syndrome, the first step is to stop giving your child the food(s) that seem to trigger a reaction, and anything else in the same category, and contact their doctor, who will likely refer your family to an allergist. An allergist will review your child’s health history, especially their history of pollen allergies and potential food reactions. They might also conduct a skin prick test or oral challenge with raw fruits or vegetables to determine a diagnosis.

What is the treatment for oral allergy syndrome?

There are a variety of ways to manage oral allergy syndrome, such as avoiding eating the trigger foods raw, especially during allergy season. Other methods for reducing cross-reactions include cooking the foods, eating canned food, and peeling the food before eating, as the offending protein is often concentrated in a fruit or vegetable’s skin. However, at the Southern California Food Allergy Institute, our mission is for people to reach true Food Freedom, meaning they can eat whatever they want, whenever they want, without fear of reaction.

Our Tolerance Induction Program (TIP™) has treated over 12,000 children with a 99% success rate by using trillions of data points to create customized treatment plans for each child. Their allergies are mapped out to form an individualized program that builds tolerance to the unique proteins each child is allergic to, all before introducing their most anaphylactic allergen. This ensures patient safety, and over time, alters their immune system to not react to their allergens.

Learn more about the TIP™, and how it can help your child with oral allergy syndrome achieve true Food Freedom!