Oral Allergy Syndrome: The Hidden Allergy

Are you or your child one of the thousands of people who experience itching or swelling inside your mouth or throat when you eat fresh fruits or vegetables? Do you also have seasonal allergies to tree, grass, or ragweed pollen? If so, you likely have oral allergy syndrome (OAS), also known as pollen-food syndrome.

People who suffer from seasonal allergies develop itching of their eyes and nose, runny nose, and nasal congestion when they breathe in outdoor pollen. Many fresh fruits and vegetables share similar proteins with these pollens and can ‘confuse’ the immune system when eaten.

The good news is that this is very different from traditional food allergy, in which people form an immune (IgE) response against a food and reactions can progress to cause severe symptoms called anaphylaxis.  Unlike food allergy, symptoms of OAS rarely progress past the mouth or throat, typically resolve rapidly, and do not require treatment.

There is no current treatment for food allergies other than strict avoidance. However, the cross reactive proteins causing OAS are very fragile and can easily be destroyed by cooking, peeling, or canning the fruit or vegetable. This is why people with tree pollen allergy may have itching when they eat fresh apples but can eat apple pie all day (not advised for nutritional reasons!) without any problems.

Diagnosis of OAS begins with establishing a diagnosis of seasonal allergies, typically by having a suggestive history followed by skin prick testing to inhalant allergens. Allergic reactions to fruits and vegetables are rare but can occur, so any symptoms more than itching in the mouth or throat should be discussed with a board certified allergist to help decide whether strict avoidance and self-injectable epinephrine should be prescribed.

Treatment of OAS begins with making the right diagnosis, which can really help patients understand the cause of their itching and ways to avoid it. Many people only experience symptoms during their pollen season, whereas others are bothered throughout the year.  General recommendations include avoiding the fresh form of the fruit or vegetable that causes symptoms and any processing, especially heating (also canning or peeling), can prevent symptoms most of the time. Rarely, complete avoidance is necessary.

Although not everyone with a pollen allergy experiences OAS, these are the more common cross-reactive allergens:

• Birch tree pollen: apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, plum
• Grass pollen: celery, melons, oranges, peaches, tomato
• Ragweed pollen: banana, cucumber, melons, sunflower seeds, zucchini