When the conversation turns to food allergies, you'll hear lots of
folk wisdom: "Food allergies are common." "Many foods can
cause allergic reactions." "Don't worry about food allergies
— you just outgrow them." "Food allergies are never
serious."
The facts contradict these common notions:
- Only about 1 percent of Americans have genuine food allergies.
Even so, about 20 percent believe that they have such allergies.
- Ninety percent of food allergies involve just a few substances —
proteins in cow's milk, egg whites, peanuts, wheat or soybeans.
- It's true that children are 10 times as likely as adults to have
food allergies. And by age 6, children usually outgrow allergies to
milk, wheat and eggs. But some allergies — including those to nuts
and shellfish — can persist for a lifetime.
- Though uncommon, food allergies can lead to a life-threatening
allergic response called anaphylaxis.
James T. Li, M.D., a specialist in allergies, asthma and immunology
at Mayo Clinic, Rochester, Minn., spoke with Oasis about food allergies.
Oasis: What is a food allergy, and how does it differ from
food intolerance or food poisoning?
Dr. Li: Some people can experience a host of
troubling symptoms after eating certain foods. Among these symptoms are
stomach upset, heartburn, hives, swelling, nasal congestion and
diarrhea.
However, we must differentiate food allergies from other types of
problems that foods can cause. From a medical standpoint, we use the
term "food allergy" to mean a special type of immune system
reaction to a food substance. This reaction involves allergy-producing
antibodies that the body of a sensitized person makes. When these
antibodies come into contact with an allergy-causing food, we see
symptoms typical of an allergic reaction.
Though we see many people with a variety of problems associated with
food, only a small proportion of those problems involve this allergic
type of reaction. Many of the other types of symptoms that food can
cause — heartburn, diarrhea, gas and more — don't involve food
allergies at all.
Oasis: What are some common food allergies?
Dr. Li: Allergies to nuts, peanuts, shellfish and
fish are common, especially in adults. Children can have these
allergies, and they also may have allergies to milk, soy or wheat as
well.
Oasis: What are common symptoms of food allergies?
Dr. Li: The symptoms due to a food allergy — when
we use the term strictly — are fairly typical. These include:
- Skin problems, including itching, hives or welts.
- Swelling of the lips, hands or face.
- Digestive symptoms such as nausea, cramps and diarrhea.
- Respiratory symptoms, including wheezing or shortness of breath.
- Lightheadedness, dizziness, fainting.
I would emphasize that when digestive symptoms occur alone, they do
not necessarily mean that an allergic reaction is occurring.
The most serious consequences of a food allergy would include
dizziness, lightheadedness and loss of consciousness.
Oasis: When do you need to call a doctor about food
allergies?
Dr. Li: Consider getting medical attention in two
different settings. The first is when the allergic reaction is actually
occurring. Seek medical attention immediately when you notice breathing
difficulties, dizziness or lightheadedness and swelling — especially
swelling of the lips, tongue and upper airway. Certainly you'll need to
call for emergency help when someone loses consciousness.
Second, call your health care provider if you have experienced
symptoms of an allergic reaction to food. It's important to see a doctor
who can help you discover the nature of the problem and how to deal with
it. This kind of evaluation can occur during a scheduled office visit.
Oasis: How are food allergies diagnosed?
Dr. Li: Through a careful medical history, your
doctor will try to obtain as many details as possible about the
reaction, as well as details about your general health.
Usually your doctor also will conduct a physical examination.
However, we don't expect any particular physical findings during an
examination for food allergies unless you are having a reaction at the
time of the exam. We do the examination mainly to exclude other types of
medical problems.
We also do allergy skin testing or allergy blood tests that can help
us make or exclude the diagnosis of food allergy. In the setting where a
food allergy is suspected, positive allergy tests confirm the diagnosis.
Negative (normal) skin test results would indicate that a food allergy
is probably not the cause of the "reaction."
There are quite a few misconceptions about food allergies. The bottom
line is that it's important for us to get the diagnosis right.
Recommendations for treatment are based on that diagnosis. These
allergies are often over-diagnosed by people having problems with food
and even sometimes by their doctors.
Oasis: What are the main options for treating food allergies?
Dr. Li: Once we've made a diagnosis of food allergy
and have identified the food causing the allergic reaction, the main
piece of advice that we give people is to carefully avoid that food
substance. This is easier said than done. Some food substances that
cause allergic reactions, such as peanuts, are found in prepared foods
sold in grocery stores or in restaurant-prepared meals. You wouldn't
know about these substances unless you ask about them or read labels
carefully.
Since avoiding the offending food is really the main issue, we have
to make the right diagnosis. It's a shame for people who don't have a
food allergy to fear an allergic reaction and to avoid a certain food
when they could actually eat that food without problems.
For many people — especially those with more serious food allergies
— we prescribe a kit for self-administered epinephrine (adrenaline).
Epinephrine acts to help open the airway and maintain blood pressure in
someone having a severe reaction. We want to make sure these people are
equipped for an emergency and feel confident that they know how to deal
with an allergic reaction should it occur.

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