In most people, OAS is a relatively mild allergic response, and people who have it can eat the vegetables or fruits that cause inflammation and itchiness in their throat and mouths – as long as those foods are cooked.

The reason for this? OAS sufferers are only allergic to the “heat labile proteins” – the proteins in the fruit that get destroyed once exposed to heat.

This explains why the symptoms are confined to the mouth: “When you eat the fruit raw, it’s your own body’s heat that breaks down the protein, which is why the reaction doesn’t move beyond the mouth,” says Dr. Paul Keith, an associate professor of allergy and clinical immunology at McMaster University in Hamilton, Ontario.

So while a raw apple a day might keep the person with OAS away, she can eat a slice of apple pie without a problem. The same goes for vegetables. While celery or carrots and dip may make your lips puff up, a nice hearty vegetable soup will go down smoothly.

There are some tricks you can use to try to cheat nature – but they may not work for everyone. Dr. Bruce Mazer, director of the division of allergy and immunology at the Montreal Children’s Hospital and associate professor at McGill University in Montreal, suggests microwaving the fruit, like an apple, for a few seconds.

He also suggests sprinkling lemon juice on the raw fruit and letting it sit for a few minutes before eating. These tricks may help to break down those heat labile proteins while still allowing the fruit to be somewhat crisp. You can also simply try peeling the fruit first since most of the fruit’s proteins are in its peel. Of course, this would only help for fruits that have a peel and not for fruits like raspberries and strawberries.

Dr. Keith approaches management from a different angle. He suggests trying to better control the hay fever so that your body will no longer recognize the offending proteins, even in the related fruits and vegetables. This can be done by using saline nasal sprays to keep the nose clear, wearing glasses to protect the eyes, and keeping windows and doors closed to lessen exposure to pollens.

Peanuts are the most common legume that people will react to, and about 5 per cent of peanut allergic people will react to other legumes, such as beans, peas chickpeas and lentil.

In general, food allergy is on the rise in North America and other developed countries. In Canada, an estimated 7.5 per cent of people have food allergies, representing more than 2.5 million people. In the United States it’s estimated that 12 million Americans (or just under 4 per cent of the population) have food allergies.

A major study in the United States recently found that cases of peanut allergy in children more than tripled in a decade, and that more than 3 million Americans now have a peanut or nut allergy.

Here are the rates of some of the major allergens in Canada and the U.S.

CANADA

Source: Surveying Canadians to Assess the Prevalence of Common Food Allergies and Attitudes towards Food LAbelling and Risk (SCAAALAR) study. Published in the Journal of Allergy and Clinical Immunology, June 2010.

UNITED STATES

Peanut, Tree Nut or both:
Children -  2.1 %
Adults – 1.3 %

Source: US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow-up. Published in the Journal of Allergy and Clinical Immunology, June 2010.

Milk and egg allergy are both common in children. In the United States, 2.5 per cent of children under the age of 3 have a milk allergy. Egg allergy affects 1.5 to 3.2 per cent of children.

The good news is many children outgrow their allergies to milk and egg.

Source: AAAAI

OAS is a condition that’s linked to hay fever, which affects a third of the population, so it’s not wonder that so many people are also affected by OAS.

A less severe form of food allergy, called oral allergy syndrome, is a reaction to proteins in common raw fruits, vegetables, nuts and seeds. It’s called “oral allergy” syndrome or OAS because its symptoms are usually limited to the lips, mouth, tongue and throat.

Estimated to affect about one-third of pollen allergy sufferers*, oral allergy sydrome (sometimes called pollen allergy syndrome) is more widespread than the higher profile – and more dangerous – allergies to peanuts, dairy and eggs.

If you have oral allergy syndrome, chances are that you also have allergies to pollen from trees such as birch and alder, and/or to pollens from ragweed and grass.

Think of it as an allergy by association – or a cross-reaction – because your immune system, already primed to attack tree, plant and grass pollens, does not recognize the subtle differences between their proteins and those contained in foods as basic as an apple.

Not Usually Life-Threatening

One reason for oral allergy syndrome’s lower profile is that, unlike other food allergies, its symptoms are not usually life-threatening. Another is that it is relatively easy to avoid.

“You may eat something that contains traces of peanut, dairy or egg, but you aren’t going to unknowingly bite into a raw apple,” notes Dr. Antony Ham Pong, an allergist and based in Ottawa.

High Incidence of Oral Allergy Syndrome

About 10 per cent of the population**, or roughly one-third of North Americans with pollen-related allergies, are thought to be affected by OAS.

Ham Pong says he usually first sees patients when they’re between 8 to 10 years old. It’s not clear, however, why no more than one-third of hay fever sufferers are affected.

Next: More Serious Oral Allergy Symptoms

Little did I know then that 25 years later, grass, trees, ragweed and dust would become my sworn enemies. I was about 32 years old when the grass and ragweed allergies set in. I’d had some small rashes, then one day after playing soccer with my young sons, I was relaxing in the grass. Soon, there was an angry rash on the back of my legs that extended from the underside of my calves right up my thighs.

I had skin-prick tests and was given a long list of allergens that I had reacted to. Soon after, I started a course of allergy shots. With the weekly needle and a daily antihistamine, I fared pretty well. After about six years, I decided that the immunotherapy had done what it could – my allergic responses had been cut in half – and I stopped taking the shots. July and August remained fairly enjoyable as long as I kept up the antihistamines.

Then, in the summer of 2003, my allergies took a turn to life-threatening. One evening, I was enjoying some almonds as an after-work snack when a series of symptoms rapidly developed. Suddenly, I was sneezing, my eyes were unbearably itchy, my mouth itched as well, my tongue grew thick and I had trouble swallowing and breathing.

My husband and oldest son were at work, and my younger son was out golfing. So I drove myself to the Port Colborne Hospital about 10 minutes away. At Emergency, I was whisked in and quickly given shots of both epinephrine and antihistamine. My ears were so swollen that I could barely hear the nurse and one eye had puffed shut. The experience was downright terrifying. My symptoms subsided after about two hours.

My family doctor later prescribed an EpiPen and referred me to an allergist. It turned out that my allergies had blossomed (if you’ll pardon the expression) into Oral Allergy Syndrome. This form of allergy occurs when the immune system of a person allergic to a pollen cross-reacts to proteins in fruits, nuts and vegetables from related plant families.

My anaphylactic reaction to almonds was linked to my allergy to birch pollen, while my grass allergy set off reactions to a long list of vegetables and fruits. I had to say goodbye to oranges and melons, (including watermelon), tomatoes and kiwi. My immune system’s intolerance of ragweed affected yet another group of food: there are no bananas, zucchini or cucumbers any more for this girl.

People ask, do you still look forward to summer? Of course! However, the season requires planning. Open windows are not an option for me; we have central air conditioning now. While I love to hang laundry outdoors, that has become a no-no as pollen gets caught in fabrics. I can’t cut the grass, nor even sit on the green stuff. If I go on a picnic or relax outside, a blanket is my best friend.

Planning also means nasal sprays, eye drops and a daily antihistamine. Once I’ve sprayed, droppered and swallowed, out I go, enjoying all the Canadian summer has to offer. I also take all the precautions: reading labels on all foods I eat; asking lots of questions of servers at restaurants. I live every day at every meal by the motto, “when in doubt, go without.” And I’m fortunate to have wonderful, supportive family and friends.

There are times when not being able to eat all of the fresh fruits and veggies I once enjoyed gets me down. But I am thankful for the few that I can eat and, yes, I have been known to hog my strawberries. So when you’re outside on a hot day this summer, enjoying a juicy piece of watermelon and wiping off your chin, think of me and remember how lucky you are.

Carolyn Purnell lives on the property she grew up on near Port Colborne, Ontario.

First published in Allergic Living magazine.
© Copyright AGW Publishing Inc.
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A life with OAS means only cooked or baked fruit. Crisp, raw fruit, how I miss you.

Cradling a fresh, succulent peach in my hands, I take in its tantalizing aroma. I rub the fuzz lightly on my lips before taking a big, juice-dripping bite. Delicious.

I swallow, and the tingling begins. First on my tongue, then throughout my mouth and my throat. Tingling becomes itching: there is no stranger feeling than an itchy tongue. That bane of the fruit-loving, Oral Allergy Syndrome, has kicked in.

OAS (also known as pollen-food syndrome) is an allergic reaction to certain proteins in a variety of fruits, vegetables and nuts. The symptoms include itching and burning of the lips, mouth and throat. In more serious reactions, there may be swelling of the mouth, back of the throat and windpipe as well as hives.

Those of us with the condition usually develop symptoms within minutes of eating the food, and they typically dissipate in less than 15 minutes. Just enough time to make a person go a bit crazy.

For me, the itching can be counteracted by eating a neutral substance such as bread or by drinking water. Fortunately, OAS is rarely severe.

“For the majority of people, this is not a real life-threatening problem like true food allergies,” explains Dr. Bruce Mazer, director of the division of allergy and immunology at Montreal Children’s Hospital and an associate professor at McGill University.

Raw vs. Cooked
OAS sufferers react to raw fruit, but are usually able to eat the same food cooked without a problem. “Typically we see OAS in people allergic to heat labile protein, which means those proteins easily destroyed by heat,” explains Dr. Paul Keith, an associate professor of allergy and clinical immunology at McMaster University in Hamilton.

“When you eat the fruit raw, it’s your own body’s heat that breaks down the protein, which is why the reaction doesn’t move beyond the mouth, says Keith, who’s also an investigator for AllerGen, the allergy research network.

I know the raw versus cooked issue first-hand. When I eat uncooked fruits like apples, cherries, pears and my beloved peaches, they all cause itching. But bake them in a pie and I can eat to my heart’s content, without so much as a tingle.

I remember eating apples as a youngster with no problems, but then one day, my tongue got really itchy afterward. As my mother couldn’t see anything on my tongue, she assumed I was trying to get out of eating the fruit. Then it happened again, and with different fruits. Because they couldn’t see a problem, my parents thought I was just fussing. But they did stop giving me the troublesome fruits.

By my late teens, I started trying these fruits again, in small amounts. Sometimes I got an intense itch in my mouth and throat, sometimes it was minor. If I craved the juicy goodness, I’d eat the fruits anyhow – since the itch always went away.

Once, however, I ravenously ate a whole peach. This time itchiness turned to swelling: my lips got puffy and I felt like I couldn’t swallow. The episode subsided in half an hour. I was miserable, yet vindicated, since my parents finally believed there was an allergic reaction. We asked a couple of doctors, but no one could pinpoint the condition. They advised that I avoid the offending fruits like any major food allergy, and that put an end to my fruit infatuation.

Fortunately, awareness of OAS is growing. But how can you be sure if you have it?

Next Page: Diagnosing OAS