|Also Listed As:
As many as two out of five Americans believe that they have allergies to
certain foods. In point of fact, however, fewer than 1% have true food
allergies. A food allergy occurs when the body's immune system reacts to
otherwise harmless substances in certain foods. This is different from a food
intolerance, which does not involve the immune system. While most food allergies
are mild, in some cases they can cause anaphylactic shock, a serious, sometimes
life-threatening, reaction. Food allergies affect mostly young children. With
the exception of peanut allergy, the majority of children outgrow their food
|Signs and Symptoms|
Many people who think they have food allergies actually have food
intolerances. Symptoms of a true food allergy usually involve the skin and
intestines and generally begin just after eating and not longer than two hours
following ingestion of the particular food. Common symptoms
- Hives, itching, or eczema
- Nausea and vomiting, stomach cramps, indigestion, or diarrhea
- Swelling of the eyelids, face, lips, tongue, throat or other parts of
the body (called angioedema)
- Wheezing, nasal congestion, or trouble breathing
- Lightheadedness, dizziness, or fainting
When the symptoms listed above are extreme, they can be life-threatening.
Call a medical emergency response unit if you see the following signs of extreme
allergic reaction (anaphylactic shock):
- Swelling of the throat and difficulty swallowing
- Difficulty breathing
- Rapid pulse
- Dizziness, lightheadedness or loss of consciousness
- Blue color to the skin and nails
In most cases, allergies occur when an individual who has a genetic
sensitivity to certain allergens is exposed to the substance. Foods frequently
responsible for food allergies include:
- Shellfish (such as shrimp, crab, and lobster)
- Tree nuts (namely, walnuts, almonds, and pecans)
- Peanuts (which are legumes, not true nuts)
- Fruits (particularly strawberries, but also melons, pineapple, and
other tropical fruits)
- Food additives (such as dyes, thickeners, and preservatives;
monosodium glutamate [MSG] is a common food allergy in this category)
Foods that may cause intolerance include:
- Wheat and other gluten-containing grains
- Cows milk and other dairy products
- Corn products
- Family history of allergies increases your risk of having allergies,
including food allergies. If both parents have food allergies, you have a 75%
chance of having one yourself; one parent, 30% to 40% and if neither parent has
allergies, then you have a 10% to 15% chance.
- Excessive exposure to a particular food—for
example, in Japan where rice is a staple, rice is a common food allergen; in
Scandinavia the common allergen is codfish; in India, chickpeas.
A comprehensive history will be taken to find out what symptoms you
experience after eating and how soon after eating they occur. Your doctor will
also want to know how often you have had the reaction and what type of medical
treatment was needed. Even if your symptoms seem clearly related to a specific
food, your doctor may still want to do some tests to be sure that you have a
true food allergy and to verify the food or foods responsible for your allergic
The food causing the allergy can sometimes be
- Elimination and re-challenging diet (also called elimination and
provocation diet) — suspected foods are eliminated from
the diet one at a time until the symptoms disappear. If there is still a
question about what may be causing the symptoms, then individual foods are
reintroduced one at a time to see if an allergic reaction develops. (Note
- this would not be done if the allergic reaction is
considered dangerous or life threatening.) This method is not fullproof but may
be used to narrow the list of suspected foods.
- Skin testing in which a diluted amount of the food allergen is placed
under the skin; if allergic, a raised, red skin lesion will appear, generally
within 15 to 20 minutes.
- Blood tests (RAST and ELISA), which look for antibodies against the
particular food allergens.
Although there is no guarantee of success, guidelines from reputable health
agencies suggest some steps parents can take to reduce their child's chances of
having food and other allergies. If either or both parents have a personal or
family history of allergy (for example, asthma, eczema, hay fever, perennial
allergic rhinitis [allergy to animals, dust mites, or molds]) the following
measures are recommended:
- Avoiding common allergenic foods, in particular peanuts and tree nuts,
during pregnancy and the months of nursing—peanut
protein, as well as components of cow's milk, eggs, and wheat, are secreted into
- Exclusive breastfeeding—give your baby only
breast milk for the first 6 months of life; use hypoallergenic formulas to
supplement breastfeeding if needed. Not all studies on this subject agree,
however. In fact, the latest and largest study on the topic of breastfeeding and
its relationship to allergies, particular asthma, suggests that breastfeeding in
the early months of life can prevent allergies until your child is 2 years old.
But, breastfeeding may lead to an increased risk of allergies once your child is
older than 2 years.
- Delaying giving your infant solid food until 6 months of age
- Delaying giving your child common allergenic foods as follows: dairy
until age 1 year; eggs until age 2 years; peanuts, nuts, and fish until 3 years.
Delaying foods allows the child's gastrointestinal tract to mature.
- Once an allergy has developed, carefully avoid the offending food.
The goals of treatment are reduction of symptoms and avoidance of future
allergic reactions. Once the particular food allergy is identified, the best way
to accomplish this is by not eating that food. Treatment at the time of a
reaction varies with the severity and type of symptoms. Mild or localized
symptoms may subside without treatment. Antihistamines (available either by
prescription or over the counter) are usually recommended to relieve mild
itching, swelling, rash, runny nose, or headache. Soothing skin creams may
provide some relief of rashes. Severe allergic reactions (anaphylactic shock)
can come on suddenly and accelerate quickly; in this case, you must go to the
hospital by ambulance immediately. In some instances, survival may depend on an
injection of epinephrine (adrenaline). Self-administration of epinephrine is
routinely taught tofood allergy sufferers and can be life saving. Avoiding the
offending food is the best way to prevent future allergic reactions.
- Avoid offending foods. Careful reading of all package ingredients
(many foods are processed with peanuts, eggs, or milk products such as whey);
calling ahead when eating out; and taking your own food with you on trips may be
- If you have a history of anaphylactic shock, you should keep a
preloaded syringe of epinephrine with you. Your doctor will teach you and a
close family member how to use it in case the need arises. Plus, you should wear
a medical bracelet or necklace indicating your particular food allergies.
- Antihistamines—for mild itching, swelling,
rash, runny nose, or headache; available both by prescription and over the
counter in many cold, sinus, and allergy remedies. These include
diphenhydramine, cetirizine, clemastine , chlorpheniramine, desloratadine,
fexofenadine, hydroxyzine, and loratadine. Possible side effects include
drowsiness, irritability, dry mouth, and heart palpitations.
- Skin creams—to soothe rashes
- Epinephrine injection—for anaphylactic shock.
If you have a food allergy that causes such a serious reaction, your doctor will
have you carry an injectable epinepherine pen and teach you, and those with whom
you spend a lot of time, how to use it in case of emergency.
|Nutrition and Dietary Supplements|
Although it will be necessary to diligently avoid foods that provoke an
allergic reaction, it need not restrict variety in your diet. Studies show that
the vast majority of people are allergic to only one or two foods. However, you
may be cautioned to be aware of the families of foods to which you are allergic.
For example, if you are allergic to walnuts, you may also be allergic to pecans
and almonds; an allergy to shrimp may also mean an allergy to crab.
L. acidophilus are bacteria that inhabit the intestines and vagina and
protect against the entrance and proliferation of organisms that can cause
disease. Some experts suggest that L. acidophilus may help to lower the
risk of allergies, including food allergies.
Although scientific evidence is lacking, lipase (a digestive enzyme
responsible for the breakdown of fat) has been used by trained clinicians to
treat food allergies.
Although the information to date is limited, some experts believe that
vitamin C may be helpful for allergic conditions such as food allergies. This
application needs further study, but may be related to the ability of vitamin C
to improve immune function.
Herbal medicines have not been specifically tested for food allergies. There
are a wide variety of herbs, however, that a qualified herbal specialist might
consider to help treat your food allergies and your symptoms based on his or her
clinical experience. Examples of some herbs such an expert might select are
listed below. Each of these herbs might be considered because of its ability to
treat either allergies in general or stomach symptoms:
- Chamomile, German (Matricaria recutita)
- Dandelion (Taraxacum officinale)
- Evening Primrose (Oenothera biennis)
- Flaxseed (Linum usitatissimum)
- Peppermint (Mentha x piperita)
Herbs, like medications, may produce side effects or interact with other
substances including drugs. They should, therefore, be used with caution and
only under the guidance of a professionally trained and qualified
The American Academy of Medical Acupuncture endorses the use of acupuncture
for allergies such as food allergies. Acupuncture can help restore normal immune
Although very few studies have examined the effectiveness of specific
homeopathic therapies, professional homeopaths may consider individualized
remedies for the treatment of food allergy based on their knowledge and
experience. Before prescribing a remedy, homeopaths take into account a person's
constitutional type. A constitutional type is defined as a person's physical,
emotional, and psychological makeup. An experienced homeopath assesses all of
these factors when determining the most appropriate treatment for each
Women who have a food allergy or a partner with a food allergy may be able to
reduce the risk of allergy in their child by avoiding common allergenic foods
during pregnancy and nursing.
|Prognosis and Complications|
Food allergies may cause symptoms ranging from mild abdominal discomfort to
life-threatening anaphylaxis. The avoidance of offending foods may be easy if
the food is uncommon or easily identified. However, the successful avoidance of
offending foods often requires strict reading of all package ingredients and
detailed inquiries when eating away from home. Children may outgrow food
allergies (particularly to milk or soy), but adults are unlikely to lose their
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|Review Date: December 2002|
|Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD,
Department of Internal Medicine, Newton-Wellesley Hospital, Boston, Ma and
Senior Medical Editor A.D.A.M., Inc.; Peter Hinderberger, MD, PhD, Ruscombe
Mansion Community Health Center, Baltimore, MD; Richard A. Lippin, MD,
President, The Lippin Group, Southampton, PA; Terry Yochum, DC, Rocky Mountain
Chiropractic Center, Arvada, CO.|
Copyright © 2004 A.D.A.M., Inc
The publisher does not accept any responsibility for the accuracy of
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of any of the information contained herein, including any injury and/or damage
to any person or property as a matter of product liability, negligence, or
otherwise. No warranty, expressed or implied, is made in regard to the contents
of this material. No claims or endorsements are made for any drugs or compounds
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