Image: Cantaloupe
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If you're one of the millions allergic to ragweed, you may also get a reaction to certains foods, such as cantaloupe, that contain similar proteins as pollen.
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msnbc.com contributor
updated 6/24/2010 2:19:42 PM ET 2010-06-24T18:19:42

The road to health usually means eating lots of fresh fruits and vegetables. But that might not be the case if you suffer from seasonal allergies.

People with seasonal allergic rhinitis — which affects one in five Americans — know that when the pollen count rises in the spring and fall they’ll be tormented by chronic sneezing, a stuffy or runny nose, watery eyes and sleep problems. But what many people may not realize is that the same chemicals that cause hay fever may also trigger a reaction to certain raw foods.

“As many as one-third of the people with seasonal allergies experience oral allergy syndrome,” says allergist Dr. Clifford W. Bassett, medical director of Allergy and Asthma Care of New York, and vice chairman of public education at the American Academy of Allergy, Asthma and Immunology.

This type of cross-reactivity — which occurs when a pollen allergy also causes a reaction to food that contains a similar protein chemical — is not widely understood beyond allergy specialists, says immunologist Dr. Hannelore Brucker, who treats many seasonal allergy patients patients with food-related issues in her practice at the Southdale Allergy and Asthma Clinic in Minneapolis. Patients who see a regular doctor for their hay fever symptoms and especially those who self-medicate with over-the-counter remedies are less likely to be aware of it.

Immune system in overdrive
During an allergic attack caused by inhaling pollen in grass, weeds or trees, the immune system goes into overdrive by overproducing histamines and other chemicals. Vegetables and fruits that contain the very same proteins, called profilins, found in various pollen culprits can also cause a similar, localized reaction. That is, when a child or adult eats an offending food, the body's immune system responds as if it were actually ingesting pollen.

Typical symptoms of oral allergy syndrome include a sudden tingling or swelling in the lips, mouth or throat. Other symptoms may be gum, eye or nose irritation. Some rare reactions may be more serious, including shock.

Fortunately, not all allergy patients are sensitive to all the foods that contain pollen-related proteins. Some people react to just one or two foods. But, unlike nasal allergies which are usually limited to high pollen seasons — from April to June and mid-August to the first frost — the food reactions can happen all year.

“Once your body is allergic to pollen, the allergy to the corresponding food continues, even if there is no pollen present,” Brucker says. “The mechanism is the same. Either way, you’re allergic to the same protein.”

The protein in ragweed pollen is also related to the chemicals in cantaloupe, banana, sunflower seeds, zucchini and cucumber. Grass pollen is related to peaches, celery, melons, tomatoes and oranges.

Birch pollen is related to a large number of vegetables, fruits and nuts, including potatoes, celery, walnuts, apples, pears, peaches and cherries and other pitted fruit.

Some highly sensitive people can experience swelling of the hands simply by peeling raw potatoes, says Brucker.

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Not the same as food allergy
If you don't want to give up your favorite vegetable or fruits, thoroughly cooking them changes the food’s protein structure, thereby rendering the offending foods harmless, says Brucker. Although you might get a reaction to raw cherries, the fruit may not affect you baked in a pie. But she advises allergy sufferers to check with a doctor before continuing to eat foods, even cooked, linked to their allergy.

Video: Coping with spring allergies Peeling the fruit or vegetable may not help, either. “The proteins may be found throughout the fruit and vegetable, not just near the skin,” says Brucker.

Although both food allergies and oral allergy syndrome pose problems for those who are affected by them, there's a difference in the severity of the response. People with oral allergy syndrome have reactions that are mainly in the mouth or lips. But with a serious food allergy, the whole body reacts. Itchy eyes and flushed warm skin can quickly progress to a swelling of the throat and bronchial tubes, says Brucker.

"This, in turn, can shut down the airways, leading to a life-threatening situation," she says.

Oral allergy syndrome symptoms are rarely seriously dangerous. But it's important to be aware of a possible reaction to the food triggers.

“In some cases, the oral allergy syndrome experienced by people with seasonal allergies can progress into a food allergy,” Bassett says.

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