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Advice from your Allergist
Here's some food for thought.
Allergies, including hay fever, asthma and skin disorders, affect 58.7 million Americans or 25%
of the population. Although the true incidence of food allergy is unknown, a recent study suggests
that about 5% of the population may suffer from adverse reactions to food.
Historical records show that people have long been ware of food allergy. Hippocrates noted that
cow's milk could cause gastric upset and hives. The Roman poet Lucretius said, "One man's meat is another
man's, poison." And some scholars believe Old Testament dietary restrictions were based upon the
awareness that certain foods could cause adverse reactions. However, the serious study of food allergy
began at the start of this century. Since then, research has led to effective procedures for the diagnosis
and treatment of food allergy, relieving the symptoms of millions with this problem.
What are some common symptoms of food allergy?
Vomiting, nausea, stomach cramps, indigestion, diarrhea, hives, eczema, headaches, asthma, earaches and
rhinitis (itchy, stuffy, runny nose; sneezing, and phlegm in the throat) are among the most common symptoms.
In fact, many parts of the body can be affected by food allergy. The frequency and severity of
symptoms vary widely from one person to another. Highly allergic persons may experience severe and life
threatening reactions such as upper airway swelling of the tongue and lips while, in milder
cases, others may only suffer a minor case of sniffles. Because these symptoms can be caused by a
number of diseases, your allergist may want to examine you to rule them out as the source of your problem.
Not all adverse reactions to foods are due to allergy. Some reactions to milk, for example, are related to
a deficiency of an enzyme (lactase) which normally breaks down a sugar in milk (i.e. lactose).
This deficiency in some individuals causes a reaction similar to food allergy when milk is ingested.
What causes my symptoms?
Allergy is caused when your body's immune system over-reacts to the introduction of offending substances.
Normally, your body's defense mechanisms (antibodies) keep you healthy by fighting such invaders as
bacteria and viruses, which can cause infections, and inactivating allergens, which ran cause allergic
reactions. The body produces several types of antibodies, or immunoglobulins. When antibodies battle with
allergens, chemicals, including histamine, are released as a part of the body's reaction to these
substances. One anti-body in particular, immunoglobulin E or IgE for short is produced in greater
quantities than normal by persons with allergies. In large amounts, IgE released chemicals can cause
blood vessels to widen, smooth muscles to contract and affected skin areas to become red, itchy and
swollen, resulting in an allergic reaction. In fact, these IgE antibodies found in tissues and secretions
are thought to be responsible for classic allergy symptoms such as hives, swollen nasal membranes, diarrhea
Why me? Why have I developed food allergy?
You probably inherited it. Heredity seems to be the prime reason some people have allergies and others
don't. If both your parents have allergies, you have a 75117c chance of being allergic. If one parent is
allergic or you have relative on one side with allergies you have a 5017c chance of becoming allergic.
Although food allergy occurs most often in infants and children, it can appear at any age and can be
caused by foods that have been eaten for years without any problems.
Other factors also come into play. For instance, excessive exposure to a particular food may create
sensitivity to that food as testified to by the high incidence of fish allergy among Scandinavians and of
rice allergy among the Japanese.
Some foods are more potent allergens than others. More people suffer reactions from peas than from
carrots, from citrus fruits than from pears. Also, your reaction to a particular food can be affected by
your physical condition at the time. If you have a cold, an upset stomach or a non-food allergy hay fever,
for example, during high pollen season you may be more susceptible to food allergy. Emotional stress also
may aggravate allergic symptoms.
What foods are most likely to cause allergy?
Eggs, milk, nuts, soy, seafood, fish, corn and wheat are the most common allergy causing foods,
but almost any food can cause allergy. Keep in mind that if you are allergic to a particular food,
you might be allergic to related foods. For example, a person allergic to avocado also may react to bay
leaves because they're in the same botanical family. Likewise, a person allergic to peanuts often cannot
tolerate other members of the legume family whose members include peas, beans and licorice.
How do allergists determine which foods make me sick?
The procedure varies from patient to patient. Some persons know exactly what food causes their allergies.
They eat strawberries and immediately break out with hives, or they drink milk and immediately begin
vomiting or get diarrhea. Sometimes, however, they need their allergist's help in determining the "culprit,"
especially when symptoms show up man hours after ingesting an offending food.
Your allergist may begin by taking a detailed history. He'll look for clues in your lifestyle that
will help pinpoint the cause of your problem. You'll be asked about your work and home environments,
your eating habits, your family's medical history and miscellaneous matters, such as what kind of heating
and cooking fuels you use, and if you have pets.
But some of these questions don't have anything to do with food!
These questions are necessary because your allergist wants to eliminate the possibility that another
problem or multiple allergies may be causing your symptoms. For example, a patient's allergy to pollen or
mold may trigger his allergy to eggs, so that in the summer, when mold and pollen are everywhere he may not
be able to eat eggs even though he can eat them safely the rest of the year.
What's next, after taking history?
You may require some tests. Your allergist may employ skin testing, in which small amounts of the
suspected allergen are introduced into the skin. A positive reaction a wheal, swelling or flare in the
surrounding red area indicates the presence of allergic antibodies.
Some patients are given RAST tests, which use blood samples to determine the extent of antibody product
against an allergen.
Will these allergy tests pinpoint my problem?
Although these tests give your allergist further clues for the diagnostics, they are not 100% reliable.
With the information gained from your history, physical exam and the tests, your allergist may further
narrow down the suspected foods by placing you on a special diet.
If your symptoms occur only occasionally, the culprit is a food that is eaten infrequently.
Your allergist may ask you to keep a daily food diary listing all food and medication ingested,
along with your symptoms for the day. By comparing "good days" with "bad days," you and your allergist
can determine which foods are prime suspects.
Then you may be asked to follow a trial diet, which alternates days of consumption and avoidance of
suspected foods. If your symptoms subside during abstinence - and flare up when you eat the food again -
the problem food has been identified.
But I have allergy symptoms every day. How do my allergist and I begin to identify what foods
I'm allergic to?
Your allergist may ask you to go on an elimination diet tailor made for you.
You may be asked to eliminate foods implicated on the basis of your history, foods known to
be highly allergenic and foods indicated in positive skin tests. After several weeks on the elimination
diet, your system should be cleared of allergenic foods. When your symptoms cease, your allergist may
reintroduce foods one at a time to your diet, and watch for reactions.
This reintroduction is called a "challenge." Many challenges may be necessary to identify which foods
are safe for you and which will make you sorry. In some cases, not all offending foods or additives can be
identified. Then your allergist may prescribe drugs to ease the symptoms.
Once my allergy is identified, how is it treated?
Avoidance of the allergenic food is the best policy. You must be vigilant in checking ingredient labels of
food products to make sure an offending food or food additive is not present. For example, a person
allergic to milk must avoid ice cream, cheese, chocolate bars, many cake mixes, and luncheon meats in
which milk is used as filler. If you are allergic to fish, be aware that glue on envelopes sometimes
is made with fish products and could cause an allergic reaction. Special food allergy cookbooks are widely
available. Your allergist can recommend some to you.
Will I ever be able to eat these foods again?
If you have a severe immediate type reaction to certain foods, NEVER taste them again. In some very
sensitive persons a small taste of an allergenic food can produce a life threatening reaction.
However, if your symptoms are milder, you may be able to try a problem food again.
After you have abstained of at least six months or longer, your allergist may suggest that you try a
small portion of a problem food. If you have no reaction, you may be able to eat this food occasionally
and in moderation. Allergic reactions to foods have been known to disappear for months or years then
reappear. In some cases, the allergy disappears for good.
If you use caution and carefully follow your allergist's advice, you can bring your food allergy
under control. If you have more questions, consult your doctor.
Source: Palo Alto Medical Foundation
Adapted by Editorial Staff, June 2007
Last update, August 2008