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Oral Allergy Syndrome

Oral Allergy Syndrome to Fresh Fruits and Vegatables

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Updated July 10, 2009

Updated July 10, 2009

What is the Oral Allergy Syndrome?

The oral allergy syndrome (OAS) is caused by cross-reactivity between proteins in fresh fruits and vegetables and pollens. This syndrome occurs in a large number (up to 70 percent) of people with pollen allergy. The proteins in the fruits and vegetables causing OAS are easily broken down with cooking or processing. Therefore, the OAS typically does not occur with cooked or baked fruits and vegetables, or processed fruits such as in applesauce.

What Symptoms Occur with OAS?

Most people with OAS have symptoms such as itching, burning, tingling and occasion swelling of the lips, mouth, tongue and throat where the fresh fruit or vegetable touched. Symptoms usually only last a matter of seconds to a few minutes, and rarely progress to anything more serious.

However, some studies have shown that up to 9 percent of people with OAS may experience more severe symptoms of food allergy, and up to 2 percent may experience anaphylaxis. It is for this reason that some authorities suggest changing the name to pollen-food syndrome. Symptoms are more likely to occur and be more severe during the season in which the responsible pollen is found.

What are the Associations Between Foods and Pollens?

The following fruit-pollen associations have been shown in people with OAS. People with allergy to these pollens often experience symptoms of OAS if the fresh fruit or vegetable is eaten:
  • Ragweed (weed): melons (watermelon, cantaloupe, honeydew), bananas, cucumbers and zucchini.
  • Birch (tree): potatoes, carrots, cherries, celery, apples, pears, plums, peaches, parsnip, kiwi, hazelnuts and apricots.
  • Mugwort (weed): celery, carrots, various spices.
  • Grasses: tomatoes, potatoes, peaches.

How is OAS Diagnosed?

OAS is diagnosed when there is a history of the above symptoms in people with seasonal allergic rhinitis with pollens as a trigger. Positive skin testing to the suspect food can confirm the diagnosis of OAS, although food skin testing extracts obtained commercially will commonly be negative since the proteins resulting in OAS are broken down during processing. Therefore, it may be necessary to use the fresh fruit or vegetable to skin test, called a “prick-prick” procedure. The skin-testing needle is inserted into the fresh food, then used to prick the person’s skin.

How is OAS Treated?

Because of the small chance for a more severe reaction, avoidance of the fresh fruits or vegetables is advised. Many people already avoid the suspect foods since the symptoms are uncomfortable. Usually, the fruits and vegetables are tolerated in cooked, baked and processed forms. A few studies have shown that allergy shots to the cross-reacting pollens can reduce or eliminate the OAS symptoms.

What to learn more? Find out more about food allergies.

Sources:

Sicherer SH. Clinical Implications of Cross-Reactive Food Allergens. J Allergy Clin Immunol. 2001; 108:881-90.

Ortolani C, Ispano M, Pastorella EA, Ansaloni R, Magri GC. Comparison of Results of Skin Prick Tests and RAST in 100 Patients with Oral Allergy Syndrome. J Allergy Clin Immunol. 1989; 83:683-90.

Sampson HA. Adverse Reactions to Foods. In: Adkinson NF, Yunginger JW, Busse WW, et al, eds. Middleton’s Allergy Principles and Practice. 6th edition. Philadelphia: Mosby Publishing; 2003:1619-1643.

DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.

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