Oral Allergy Syndrome

lip allergy
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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, 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 occasional swelling of the lips, mouth, tongue, and throat where the fresh fruit or vegetable touched. Symptoms usually only last from 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 the 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 an 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 fresh fruit or vegetable to the skin test. 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 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.

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Article Sources
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