People who feel a tingling or burning sensation when they bite into a piece of fruit aren't likely reacting to pesticides – they're probably allergic to its enzymes, doctors say.

Farheed Kahn, who suffers seasonal allergies to pollen, says she gets a similar response when exposed to fruit – especially apples and oranges.

• INDEPTH: Seasonal allergies

Farheed Kahn's mouth swells when she eats apples and oranges.
(CBC)

"It just brings out the same sort of reaction," said Kahn, who lives in the southern Ontario city of Mississauga.

"My throat is swollen, my lips are swollen, I can't breathe."

'They get hay fever in their mouth, basically'

Dr. Stuart Carr says oral allergy syndrome is often unrecognized in patients. (CBC)

She's not alone. Doctors say about half of those with seasonal allergies will have some kind of reaction to fruit and experience burning and swelling, especially around the mouth and lips.

"When they eat the food, their mouth mistakes it for the pollen and they get hay fever in their mouth, basically," said Dr. Stuart Carr, an allergy specialist in Edmonton.

It's called oral allergy syndrome, a secondary allergy caused when the body thinks its reacting to pollen but is actually reacting to enzymes in fruit – food that is usually considered to be good for us.

The reactions happen year-round, but can be worse in the spring when there is more pollen to trigger reactions.

Carr said the syndrome is often unrecognized and under-reported.

Many people simply assume there is something wrong with the food, blame pesticides or avoid eating that particular fruit again.

Cooking fruit often helps

Unlike peanut allergies, doctors say reactions to fruit are rarely dangerous.

Allergists say coping strategies include cooking the fruit and taking antihistamines. Khan eats apple sauce instead of a McIntosh or Red Delicious.

Patients with the most severe reactions can undergo a treatment called "pollen immunotherapy." They're given pollen shots to get their body used to the pollen and make the fruit reactions fade away.

It takes two or three years of the right dose to achieve remission, Carr said.

Khan has started getting the shots. She said her reactions aren't as bad, but she still has to avoid many fruits.