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May 2008 - Dr. Sue MacLaren
Dear Dr. Sue: Whenever I eat almonds my mouth gets itchy.
Now, I can't eat bananas! What is this? I'm worried.
Dear Reader:
It can be scary when after just a few bites and you think, “Uh oh,
my mouth is itchy. Is this the start of an anaphylactic or life-threatening
reaction? Is this it?!”
In fact, what you may be experiencing is oral allergy syndrome (OAS) or
fresh fruit syndrome: an allergic reaction that causes itchiness, redness,
tingling and swelling of the mouth after eating certain vegetables, fruits
or nuts.
Signs and symptoms of OAS generally involve the lips, tongue, mouth, back
of the throat, upper surface of the mouth (palate), and even gums. This
type of allergic reaction is based on the superficial contact of the food
protein and it usually produces mild symptoms that subside in minutes.
OAS is usually not a severe condition and medical treatment is rarely
needed.
How does it happen? You must have an allergy to pollen (the small powdery
grains from plants that are airborne), even a very mild one, in order
to be affected by OAS. This syndrome occurs in approximately 35 per cent
of people who are allergic to various pollens, especially birch and ragweed
pollen.
Why? The proteins found in some pollens are so similar to those found
in some types of fruit, nuts and vegetables, that your immune system is
unable to distinguish them. You eat the banana, which has protein resembling
the pollen protein of ragweed, and presto, it triggers the allergic cascade
reaction. Only raw or fresh fruits and vegetables cause symptoms. The
proteins are temperature sensitive. Once these foods are cooked, they
don’t cause a reaction. Even canned or frozen foods may not cause
a problem.
The exception. Nuts may trigger a reaction, whether they’re raw
or cooked. People with birch tree pollen allergies most often react to
the following foods: apples, apricots, carrots, celery, cherries, coriander,
fennel, kiwi, nectarines, parsley, parsnips, peaches, pear, peppers, plum,
potatoes, prunes (an often necessary fruit!), and northern tree nuts (hazelnuts,
filberts, almonds (I love almonds!) and walnuts.
Those with allergies to ragweed pollen react to bananas, melon (watermelon,
cantaloupe, honeydew), and members of the gourd family (cucumber, zucchini
and squash). People with ragweed allergy may also cross-react with sunflower
seeds, echinacea or chamomile tea.
For sufferers of allergies to grass pollen, there are reactions to celery,
melon (watermelon), oranges, peaches and tomatoes.
While OAS and a nut allergy are both types of allergic responses that
occur from nuts, the two aren’t the same. Symptoms are different
and a person may have both conditions or one or the other. You may also
experience watery, itchy eyes, runny nose and sneezing.
More sensitive people may get gastrointestinal symptoms, nausea or diarrhea,
as the food passes through the body. In extreme cases and very rarely,
a life-threatening condition called anaphylaxis may occur. This is the
scary one! Occasionally, some individuals will have a serious response
to OAS. Although it’s rare, this reaction may include an asthma
attack.
How to diagnose OAS. Your health care provider will take a thorough history
and conduct a physical. The gold standard is skin testing done by an allergist
who pricks or scratches the skin with the pollen extract.
Treatment. Most importantly: avoid the offending food. Goodbye bananas!
Cooking the food also eliminates the allergic nature, but nuts are the
exception; they can trigger a reaction whether raw or cooked. Eat frozen
fruits and vegetables as well as canned and dried. Options for drug treatment
are antihistamines but they’re generally not needed because the
response is usually mild and short lived. OAS isn’t the same as
a true food allergy. Allergy shots aren’t intended for treatment
of this condition.
So you can still enjoy those fruits and veggies; just cook, can, dry or
freeze and deliver them over those lips. Mmm, good!
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