Food allergies may mimic seasonal allergies

(CNN) -- Have you ever experienced itchiness or hives in your mouth
area after eating raw fruit or vegetables? Do you also have seasonal
allergies?

People with allergies to birch pollen may have associated allergies to
raw apples.

If so, you may have oral allergy syndrome, whose symptoms occur because
the proteins in some fruits and vegetables are similar to proteins in
some pollens.

"They're not identical proteins, but they're similar enough to confuse
the immune system to have these reactions," said Dr. Robert Wood,
chief of pediatric allergy and immunology at Johns Hopkins Children's
Center.

That's not to say that everyone with pollen allergies has oral allergy
syndrome. A person may sneeze all spring long and not have any obvious
food sensitivities.

But oral allergy syndrome may help explain why some people have
seemingly mysterious reactions to certain foods -- for example, raw
apples but not cooked apples. That's because there are proteins in raw
apples that are very similar to the proteins in birch pollen, experts
say. Read about pollen predictions for this season

Cooking the offending fruits and vegetables will "denature" or change
the shapes of these proteins, so people with oral allergy syndrome will
usually be able to eat them without a problem, said Dr. Stanley Fineman,
allergist with the Atlanta Allergy and Asthma Clinic.

Some people find that the peel of a fruit has more allergens than the
meat, so peeling first helps, Wood said.

Because the reaction is usually localized to the mouth area, including
lips, tongue, and throat, some people will choose to ignore the symptoms
and continue to eat offending foods, Wood said. For people with
reactions confined to the mouth, this is a "reasonable" choice they
could make. Learn more about managing food allergies »

"Patients will typically decide on their own, without any discussion
with a doctor, whether they enjoy the apple enough to put up with an
itchy mouth, or whether they hate the itchy mouth enough to avoid the
apple," he said.
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POLLENS AND ASSOCIATED FOODS

Ragweed: Bananas, melons (watermelon, cantaloupe, honeydew), tomatoes

Birch: Apples, carrots, celery, peaches, pears, potatoes, hazelnuts

Grass: Kiwis, tomatoes

Mugwort: Apples, carrots, celery, kiwi fruit, peanuts, some spices
(caraway seeds, parsley, coriander, anise seeds, fennel seeds)

Source: The Mayo Clinic
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But in rare cases people with oral allergy syndrome experience
anaphylaxis, a life-threatening reaction that may include blocked
airways, hypertension, anxiety, vomiting and diarrhea. The most severe
reactions require the use of an injection of epinephrine to subside,
which is why many people with food allergies carry auto-injectors for
emergencies.

Over-the-counter antihistamines alleviate symptoms of reactions for some
people, experts say.

Studies have shown that some people who undergo allergy shots for pollen
allergies will experience relief in oral allergy syndrome, Wood said,
but at this point no one should get shots just for that reason, since
they don't work on most people's food allergies.

"If you are a good candidate for allergy shots otherwise, this may be a
side benefit," he said.

While other kinds of food allergies present in the first two or three
years of life, pollen allergies that contribute to oral allergy syndrome
develop more slowly, Wood said, peaking in the teenage and young adult
years. Some people may develop allergies even later in life, he said.

A person who moves to a new part of the country, having never been
exposed to the native pollens there, may become allergic to those
pollens and have some spill-over into food allergies, Wood said.

   Typically, once people start to react to some foods, they will also
react to other foods in the same group. People may find that their
allergies to raw fruits and vegetables subside during the season when
the associated pollen levels are low. For example, a person may react to
raw apples from March to October, but feel fine when eating them from
November to February, when birch pollen is low, Wood said.
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About half of people with pollen allergies have improvement from puberty
through adulthood, which correlates with associated food allergies, Wood
said.

"The better the pollen allergy gets, in most people, the less the food
allergy will occur," he said.