What symptoms occur in an allergic reaction?
MOUTH: Itching & swelling of the lips, tongue or mouth.
THROAT: Itching and/or a sense of tightness in the throat, hoarseness and hacking cough.
SKIN: Hives, itchy rash and/or swelling about the face and extremities
GUT: Nausea, vomiting, cramping and diarrhea.
LUNGS: Shortness of breath, repetitive coughing and/or wheezing
HEART: “Thready” pulse, low blood pressure and passing out but only as a part of anaphylactic shock.
In contrast to a non-allergic adverse reaction to food (see below), symptoms of food allergy usually occur within a short time after ingestion (20-30 minutes).Symptoms may not peak as quickly, however, and will sometimes progress for hours if left untreated. The severity of symptoms can quickly change. All of the above symptoms can potentially progress to a lifethreatening situation. Non-allergic adverse reactions to foods present with different kinds of symptoms, depending on which specific disease is present. Your allergist can discuss the differences with you.
What are common food allergies?
In children, milk, egg, soy, wheat, peanut (a legume) and tree nuts are the most common IgE-mediated food allergies. In adults, tree nuts, peanut, fish and shellfish are most common. No food is exempt however.
What are some other kinds of adverse reactions to food?
The majority of adverse reactions to foods are not true allergies. There are many types of adverse reactions to food. In general, food reactions can be classified as either non-immunologic (intolerances) or immunologic (hypersensitivity reactions). The former include lactose intolerance, food poisoning, psychological (e.g., bulimia) and pharmacologic reactions (e.g., jitteriness from caffeine). The latter can be further subdivided in to allergic (“Immunoglobulin (Ig) E-mediated,” in which IgE that binds to a specific food is present in excessive amounts) or non-allergic (Celiac disease, protein-induced colitis, for example) hypersensitivity reactions. The natural history of you or your child’s food reactions depends in large part upon what type of reaction is occurring and to what food it occurs. You should discuss this with your allergist.
How are true food allergies diagnosed?
The history usually suggests the presence or absence of a food allergy. Symptoms usually start within a short time of ingestion of the offending food, although they may not peak until hours later. Onset of symptoms hours after ingestion is uncommon. Symptoms occur each time enough of the food is ingested to trigger a reaction and do not occur if the offending food was not eaten. A history suggestive of food allergy can be confirmed by skin testing, which tests for food-specific IgE in the skin. These tests have a very low “false negative” rate, but clinically irrelevant or “false
positive” tests are more likely to occur.
CAP RASTs (blood tests for food specific IgE in the blood) are a little less sensitive than skin tests. They cost more and it takes longer to get the results. With the exception of a few foods, CAP RAST levels have unknown predictive value. Discuss with your allergist if CAP RASTs are indicated in your case. You should discuss the interpretation of food skin test or CAP RAST results with your allergist. Unfortunately, the interpretation is not always “black or white.” Tests for food-specific IgG (another kind of immunoglobulin) in the blood are not known to have any diagnostic value for food reactions. In fact, many normal people have food specific IgG in their blood. Tests for IgE are not useful in diagnosing non-allergic food reactions.
In any case, the best tests to confirm the presence of any kind of food reaction are 1) what happens if the food is ingested, and 2) what happens if the food is eliminated. You should discuss with your allergist whether a food challenge or trial food elimination is safe and/or necessary in your case.
FOOD ALLERGY RESOURCES
The Food Allergy Network
10400 Eaton Place, Suite 107
Fairfax, VA 22030-2208
(708) 691 – 3179
American Academy of Asthma, Allergy and Immunology
611 E. Wells Street
Milwaukee, WI 53202-3880
(414) 272 – 6071
American College of Allergy, Asthma and Immunology
85 West Algonquin Road, Suite 550
Arlington Heights, IL 60005
(847) 427 – 1200
Asthma and Allergy Foundation of America
1125 15th St., NW, Suite 501
Washington, DC 20005
(202) 466 – 7643
For more information about MedicAlert:
2323 Colorado Avenue
Turlock, CA 95382
(209) 668 – 3333
There are numerous cookbooks in print with recipes for people with dietary restrictions. A partial list is available in our office.