Oral Allergy Syndrome


The surprising link between food & seasonal allergies.

Maureen Combs, 33, enjoyed apples her entire childhood. But around age 20, her lips started to tingle whenever she bit into a fresh apple. Then the roof of her mouth would begin to itch and a hive would develop on her lower lip and start to swell.

It turns out that her reaction to fresh apples was related to her birch pollen allergy. In the same way, someone who is allergic to grass might react to tomatoes and someone allergic to ragweed might react to cucumbers.

The culprit? Oral allergy syndrome (OAS), also known as pollen-food allergy syndrome.

People who suffer from hay fever (allergic rhinitis caused by pollen) can experience OAS when their immune system mistakes proteins in certain fruits or vegetables for the proteins found in their problem pollen. For example, when someone like Combs with a birch pollen allergy bites into an apple, the same IgE (immunoglobulin E) antibody that recognizes the birch pollen protein also recognizes a similar protein in the apple, prompting an allergic immune response, explains allergist Philip C. Halverson, MD, FAAAAI, of Allergy & Asthma Specialists in Minneapolis.

The allergic reaction causes symptoms such as itchiness, tingling or swelling of the mouth, face, lips, tongue and throat. The reaction is usually immediate, short-term and mild but OAS can cause serious reactions and anaphylaxis in rare cases.

itchy throat


“It makes things difficult. I grew up eating all of these wonderful raw foods,” says Combs, who has year-round allergies to trees, grasses, mold, dust, dander and cockroaches.

Trying new foods can be a gamble for Combs. She worries that another new food will cause a reaction as she navigates a lifestyle free of raw apples, carrots, peaches, plums, cherries, avocados, some nuts, lettuces and cucumbers—all of which might set off an OAS reaction for her.

Hay Fever & Food

Various pollens trigger hay fever symptoms and those pollens cross-react with different types of foods. Birch tree pollen, which often cross-reacts with apple, is a common OAS culprit. In fact, 50 to 75 percent of adults allergic to birch tree pollen experience OAS symptoms, according to the American Academy of Allergy, Asthma and Immunology (AAAAI).

Other hay fever triggers, such as grass pollen allergy, can cross-react when a person eats melons. And someone allergic to ragweed pollen might experience OAS from eating bananas.

Hay fever is a common ailment—about 26 million Americans reported experiencing hay fever in 2015, according the Centers for Disease Control and Prevention (CDC). So why doesn’t OAS cross-reactivity happen in everyone with seasonal allergies?

“There’s enough of a difference in the fruit and pollen proteins that the allergic antibodies don’t always cross-react,” says Halverson.

The seasonal nature of pollen allergies also can affect OAS reactions, worsening for some during the pollen season.

Cooking the foods reduces cross-reactions because high temperatures break down the proteins responsible for OAS. Peeling the food before eating may be helpful, as the offending protein is often concentrated in the skin, according to AAAAI.

What To Do

If crunching on raw carrot sticks suddenly makes your mouth tingle, it’s a good idea to get checked by your physician.

Allergy testing (skin or blood test) for the trigger foods may confirm the allergy. However, allergy testing for OAS is commonly negative, Halverson says. An OAS diagnosis is primary made on the basis of a person’s clinical history.

Avoiding raw forms of the food is the most common treatment, although some people also stay clear of the cooked version. If only one food has caused a reaction, it may not be necessary to avoid all other foods in the same family, Halverson says.

Antihistamines generally don’t help and symptoms usually resolve quickly without treatment, Halverson says. The exception is those rare cases of anaphylaxis, which require epinephrine and emergency medical attention.

While immunotherapy shots help reduce hay fever symptoms in about 85 percent of people, according to the American College of Allergy, Asthma and Immunology (ACAAI), allergy shots have not been proven effective in treating OAS, Halverson says.

Late Development of OAS

Unlike common food allergies to peanuts, milk and egg that can develop in infants and young children, OAS usually doesn’t appear until the teen or adult years, Halverson says.

Leigh Anne Tani of Surrey, British Columbia, Canada, was about 11 years old when eating apples started to make her lips and eyes swell and peeling raw potatoes left her with hives on her hands. She now avoids raw apples, cucumbers, grape tomatoes, potatoes, corn, avocados, pineapples, celery, peppers, cherries, peaches, pears and peas, although she can eat these foods cooked.

“I just learned to deal with it,” says Tani, 42, who was diagnosed with OAS in her 20s and has had seasonal allergies for as long as she can remember.



Managing OAS

In addition to figuring out a new diet and dealing with the fear a reaction can elicit, people with OAS must also navigate life with an allergy that many people don’t understand. When Nathan Alan McConnell of Houston, Texas, was diagnosed with a severe form of OAS at age 25, he found it “almost impossible” to convince the people around him of the validity of his diagnosis.

McConnell, 33, has seasonal allergies, along with food allergies to pork, soy and rice. When he eats raw plants—including fruits, vegetables, mushrooms, nuts, grains, seeds, spices and herbs—he experiences severe OAS reactions, including nausea, tightening lungs and anaphylaxis. He can eat only a limited number of cooked vegetables, such as green beans, potatoes, sweet potatoes, apples, corn and spinach. It is difficult to maintain a healthy diet, he says, especially when companies add “real fruit” to their products.

“OAS has been a consistent drain on my emotions, my body and my nutrition,” McConnell says. “I’ve watched entire aisles of the grocery store become off limits to me.”

But OAS is manageable once people understand the correlation between pollen and reactions to food, along with how to avoid the foods that are causing their symptoms.

The lack of understanding and knowledge about OAS “was very frustrating at first,” Tani says. “But OAS is not a prison sentence. Just go slowly and listen to your body.”

Contributor Wendy Mondello is a health writer. She has a teen with asthma and multiple food allergies.