Forbidden Fruit
A life with OAS means a lot of cooked or baked fruit. Ah, crisp goodness, how I miss you.
By Colleen Seto
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 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.
Diagnosing OAS
Fortunately, awareness of OAS is growing. But how can you be sure if you have it? Since it
occurs mainly in people with allergies to birch, grass or ragweed pollen, “the key to diagnosis is
the history of hay fever and positive skin tests to relevant pollens,” says Mazer. “As well, a
history of eating the food with typical mouth and throat symptoms without other symptoms, plus
the ability to eat the cooked variety of the fruit or vegetable makes the diagnosis fairly certain.”
However – I don’t react to any vegetables sharing allergenic proteins with birch tree pollen, only
to fruits. Keith explains that this could be due to a lower level of offending proteins in some of
the cross-reacting foods. As well, freshness makes a big difference to the potency. “The peel also
tends to have more protein than the fruit itself,” he says. “So if you peeled an apple and ate it,
you might not react as if you ate one with the peel on.”
Like any food allergy, both Mazer and Keith espouse avoidance as the primary means of coping.
Mazer also mentions microwaving raw fruit before eating, but agrees the suggestion is not the
most appetizing solution. Sprinkling the cut-up fruit with lemon juice and letting it sit for a few
minutes may also work.
Given the unpredictability of “true” food allergy, even I have to be on the lookout. “If someone
gets hives or worse with the fruit, vegetable or nut; or gets symptoms with both fresh and cooked
varieties; or has prolonged symptoms (hours instead of minutes), this may be the sign of a true
food allergy,” says Mazer. In those cases, he emphasizes the importance of seeing an allergist for
diagnosis and testing, and then to “strictly avoid the substance and carry self-injectable
adrenaline.”
Seeds of Control
If the problem is genuinely OAS, “the key is to manage the hay fever,” Keith says. He suggests
using an intranasal steroid two weeks before the season and throughout, to stave off a seasonal
rise in the allergic IgE antibodies.
“We want to turn off your nose’s production of IgE locally to the pollen, so when you eat a
protein that is very similar, you won’t get the symptoms,” he says. Immunotherapy or allergy
shots has not proved particularly helpful for this syndrome, though it can be effective for the hay
fever itself.
Some natural therapies may provide some relief. Keith finds that nasal rinsing with a saline spray
can be effective in reducing inflammation, while wearing glasses lessens pollen exposure in
eyes. He also recommends keeping windows closed, especially in the bedroom and the car,
during the specific allergy season.
Keith and his colleagues have recently completed a novel study on a mint tea high in rosmarinic
acid, which is believed to have anti-allergic properties. Trials were conducted with sufferers of
severe chronic rhinitis. The results, which Keith allows “are interesting” were to be released at
the American Academy of Allergy, Asthma & Immunology annual meeting in March. He thinks
it’s important to undertake proper studies “to see if natural therapies do have a benefit.”
Given that a third of Canadians suffer from hay fever, the experts actually find it surprising that
so few people experience OAS. “A major question is not why people get this problem, but why
more people don’t – since the pollen-protein link is always there,” says Mazer. It tends to be
those who have more severe hay fever who get OAS. As that doesn’t describe me, I’m likely
something of an anomaly.
“If you get OAS symptoms, see your doctor,” says Keith. “What you’re experiencing is really a
side effect of your hay fever not being controlled.” So it’s off to the specialist for me to make
sense of my hay fever symptoms. There may be a chance yet for my love affair with peaches.
One can only hope.
First published in Allergic Living magazine, Spring 2009.
For a story explaining the science of Oral Allergy Syndrome and a full chart of cross-reacting
fruits, vegetables, nuts and spices, purchase the Spring 2009 issue.
Click here to order that issue or to subscribe online.
Issue also available at Chapters, Indigo, London Drugs and Shoppers Drug Mart stores.
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