Food Allergies

Definition

Food allergies are the body's abnormal response to specific proteins found in food. These proteins normally are harmless but cause a reaction in some people. They can occur when food is either eaten or touched.

Demographics

About one-quarter of American households have a member with a food allergy. However, this statistic is derived from self-reported information rather than rigorous studies. Many people use the term “food allergy” to describe what is actually a food intolerance. A food intolerance is a reaction to food that does not involve the immune system. Lactose intolerance is a common food intolerance, while celiac disease is a food allergy.

Eight foods cause 90% of all food allergies. These are:




Close-up of the swollen upper lip of a six year-old boy caused by an allergic reaction to peanuts.





Close-up of the swollen upper lip of a six year-old boy caused by an allergic reaction to peanuts.
(DR P. MARAZZI/Science Source)

Foods that may contain common allergens

Allergen

Food product

Milk

Butter (including butter flavor, butter fat, and butter oil)

Buttermilk

Casein

Casemates

Cheese

Cream

Cottage cheese

Custard

Ghee

Goat milk

Milk proteins (lactalbumin, lactalbumin phosphate, lactoglobulin, lactulose)

Milk solids

Pudding

Sour cream

Yogurt

Eggs

Albumin or albumen

Eggnog

Lecithin

Lysozyme

Marshmallows

Marzipan

Mayonnaise

Meringue

Nougat

Pasta

Surimi (fish product)

Peanuts

Any nut product (including nut butters and oils)

Ethnic foods (especially African, Chinese, Indonesian, Mexican, Thai, and Vietnamese dishes)

Many candies and baked goods

Nougat

Sunflower seeds

Description

All food contains proteins that enter the body when the food is eaten, or in some cases if it is touched. Allergic reaction occurs when the body responds to these normally benign proteins as if they were harmful. The first time the food is consumed, the body reacts with an abnormal biological alarm. As the food is digested and broken down into proteins that enter the bloodstream, protective cells, called antibodies, are formed. Usually, antibodies are used to attack germs, such as bacteria or viruses, that invade the body. In this case, antibodies protect from disease by destroying the germs. Antibodies prompt other reactions in the body, such as a fever to kill disease cells or the dilating of blood cells so that blood can reach infected areas of the body more rapidly.

The second time the food is ingested, the antibodies alert the body that an invader is present, and the body mounts an attack. The body's response causes the symptoms of an allergic reaction.

Causes and symptoms

When the body encounters an allergen, it releases large amounts of a chemical called histamine. This release of histamine is responsible for allergic symptoms. Symptoms of food allergy can range from mildly annoying to dangerous and life threatening. These symptoms include:

The most serious symptom of food allergy is anaphylaxis. Anaphylaxis, also called anaphylactic shock, is a sudden and potentially life threatening allergic reaction in which the whole body reacts to an allergen. During anaphylaxis, the airway constricts, making breathing difficult. Swelling of the throat may block airways as well. Vomiting and diarrhea may occur. The face may swell and the skin may become itchy with a rash or hives. The heart may race and the heartbeat may become irregular.

Diagnosis

The offending food must be identified if food allergy reactions are to be avoided. To identify food allergies, a doctor will first record the patient's detailed medical history. It is a good idea for patients to keep a food diary documenting all foods eaten and when, as well as any physical symptoms and when they occurred. In most cases, patterns of reactions to specific foods can be seen in the food diary.

Other means of diagnosing food allergies include:




Eight most common food allergens.





Eight most common food allergens.

Treatment

Treatment for an allergic reaction is administration of an antihistamine drug. The most common antihistamine is diphenhydramine hydrochloride, which is found in over-the-counter drugs, such as Benadryl, and in some prescription drugs. If taken immediately, antihistamines can stop or moderate an allergic reaction.

In cases of a severe allergy or anaphylaxis, an injection of a strong antihistamine called epinephrine (also known as adrenaline) may be used. An auto-injectable form of epinephrine (Epi-Pen) that looks similar to a large ballpoint pen can be carried at all times if a person has a history of severe allergy. If a severe allergic reaction occurs, the auto-injector is held against the skin and the medication is self-administered as a shot. Epinephrine is a strong antihistamine; it often can stop anaphylaxis symptoms.

Nutrition and dietary concerns

A doctor and nutritionist should be consulted if a food allergy is suspected. Removing foods from the diet can cause an unbalanced diet that may be deficient in necessary nutrients. Since some of the most common foods that cause allergies include milk, eggs, and wheat, significant sources of protein, calcium, and fiber may be removed. With the assistance of healthcare professionals, diets can be modified and healthy substitutions identified to avoid nutrient deficiencies.

KEY TERMS
Allergen—
A foreign substance that causes an allergic reaction in some sensitive people but not in most others.
Anaphylaxis—
Also called anaphylactic shock; a severe allergic reaction characterized by airway constriction, tissue swelling, and lowered blood pressure.
Celiac disease—
A chronic digestive disorder in which eating foods that contain the protein gluten (found in wheat flour, rye, and barley) causes an immune reaction that damages the small intestine and interferes with the absorption of food.
Elimination diet—
A diet in which the patient excludes a specific food (or group of foods) for a period of time in order to determine whether the food is responsible for symptoms of an allergy or other disorder. Elimination diets are also known as food challenge diets.
Immunoglobulin (Ig)—
Also called an antibody; a substance that neutralizes specific disease-causing substances and organisms. Immunoglobulins are divided into five classes: IgA, IgD, IgE, IgG, and IgM.

Individuals following a special diet to treat other medical conditions should always consult a doctor before altering that diet. Eliminating foods from a medically prescribed diet may aggravate an existing health condition and could be harmful.

Prognosis

There is no cure for food allergies, but allergic reactions can be prevented by avoiding foods that cause an allergic response.

Prevention

It is essential that individuals with serious food allergies read the labels of every food they eat. A federal law called the Food Allergen Labeling and Consumer Protection Act (FALPCA) took effect on January 1, 2006. This law mandates that all food containing milk, eggs, fish, crustacean shell fish, peanuts, tree nuts, wheat, or soy must note this on the label.

Ingredients that may cause allergies are listed on the label after the word “Contains.” If these ingredients have names that are not readily known as versions of foods that may cause allergic reactions, the manufacturer will list the allergen in parentheses—for example, albumin (egg) or casein (milk). Additives for coloring or texture that may cause allergic reactions must also be listed.

QUESTIONS TO ASK YOUR DOCTOR

Most individuals with food allergies are allergic to only one food; however, a peanut allergy may indicate reaction to tree nuts as well. Many manufacturers who process peanut products process other nut products as well. Machines that handle and package these products may spread small pieces of peanut to other products. The FALPCA mandates that labels note this fact.

See also Artificial preservatives ; Bioengineered foods ; Celiac disease ; Childhood nutrition ; Diet apps ; Elimination diets ; Food sensitivities ; Infant nutrition ; Juice fasts ; Lactose intolerance diet ; MSG symptom complex ; Nutrisystem ; School lunches ; Whole grains .

Resources

BOOKS

Hand, Carol. Living with Food Allergies. Minneapolis, MN: ABDO, 2012.

Nelson, Carmel, and Amra Ibrisimovic. The Food Allergy Cookbook: A Guide to Living with Allergies and Entertaining with Healthy, Delicious Meals. New York: Skyhorse, 2011.

Welch, Michael J., ed. Allergies and Asthma: What Every Parent Needs to Know. 2nd ed. Elk Grove Village, IL: American Academy of Pediatrics, 2011.

WEBSITES

Li, James T. C. “What's the Difference between a Food Intolerance and Food Allergy?” MayoClinic.com . http://www.mayoclinic.com/health/food-allergy/AN01109 (accessed April 3, 2018).

MedlinePlus. “Food Allergy.” U.S. National Library of Medicine, National Institutes of Health. https://medlineplus.gov/foodallergy.html (accessed April 3, 2018).

Sicherer, Scott H. “Food Allergies.” Medscape. Updated March 16, 2018. http://emedicine.medscape.com/article/135959-overview (accessed March 26, 2018).

ORGANIZATIONS

Allergy and Asthma Network: Mothers of Asthmatics (AANMA), 8201 Greensboro Dr., Ste. 300, McLean, VA, 22102, (800) 878-4403, Fax: (703) 288-5217, http://www.aanma.org .

American Academy of Allergy, Asthma, and Immunology (AAAAI), 555 E Wells St., Ste. 1100, Milwaukee, WI, 53202, (414) 272-6071, http://www.aaaai.org .

Asthma and Allergy Foundation of America, 8201 Corporate Dr., Ste. 1000, Landover, MD, 20785, (800) 727-8462, info@aafa.org, http://www.aafa.org .

Food Allergy & Anaphylaxis Network, 11781 Lee Jackson Hwy., Ste. 160, Fairfax, VA, 22033, (800) 929-4040, Fax: (703) 691-2713, http://www.foodallergy.org .

National Institute of Allergy and Infectious Diseases, Office of Communications and Government Relations, 6610 Rockledge Dr., MSC 6612, Bethesda, MD, 20892, (301) 496-5717, TTY: (800) 877-8339, (866) 284-4107, Fax: (301) 402-3573, http://www3.niaid.nih.gov .

Deborah Nurmi, MS
Revised by Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.