Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

Food Allergy

by Rosalyn Carson-DeWitt, MD
Definition

A food allergy is an adverse or abnormal immune reaction to a food or a food additive.

Causes

A few specific foods seem to cause a majority of the food reactions. The most common triggers of a food reaction include:

  • Cow's milk
  • Eggs
  • Fish
  • Peanuts
  • Sesame seed
  • Shellfish
  • Soy
  • Tree nuts (eg, walnuts, pecans)
  • Wheat
Risk Factors

Factors that increase your chance of food allergies include:

  • History of eczema
  • History of other types of allergies, including hay fever
  • Age: young children
Symptoms

Symptoms include:

  • Skin rash, especially hives
  • Cough
  • Diarrhea
  • Gurgling stomach
  • Nasal congestion
  • Nausea
  • Severe drop in blood pressure
  • Shortness of breath
  • Skin itching
  • Stomach cramps, pain
  • Swelling in lips, mouth, tongue, throat
  • Vomiting
  • Wheezing
Diagnosis

The doctor will ask about your symptoms and medical history. A physical exam will be done. Food allergies are often diagnosed based on your own observations. It is a good idea to keep a diary of your symptoms. Note when the symptoms occur and what you have eaten.

Tests may include:

Elimination Diet

You may be asked to go on an elimination diet . This should be done under your doctor's care. You will not eat a suspected food. If your symptoms decrease or go away, your doctor may be able to make a diagnosis. If you eat the food and your symptoms come back, the diagnosis is confirmed. This is most often only done in cases of skin irritation or atopic dermatitis .

Scratch Skin Test

The doctor will place a diluted extract of the food on the skin of your forearm or back. The skin is scratched with a small pick or tiny needles. If there is swelling or redness, an allergic reaction may be present. The doctor will make the diagnosis based on the skin test and your history of symptoms. In rare cases, skin tests can have a severe allergic reaction. This test should only be used under the supervision of a physician or other trained medical personnel. Severe eczema may make this test hard to interpret.

RAST or ELISA Test

The doctor may order blood tests (RAST or ELISA). These tests measure the level of food-specific IgE in the blood. IgE is a type of protein that the body produces when it comes in contact with something to which it is allergic. The presence of IgE in the blood may indicate an allergy but is not enough to make a diagnosis.

Treatment

Avoid foods and food ingredients that cause you to have an allergic reaction. If you think you've eaten something to which you are allergic, and you have difficulty breathing, call for emergency medical help.

Treatments include:

  • Antihistamine medicine—to decrease swelling and itching
  • Corticosteroid medicine—for more severe swelling and itching
  • Epinephrine —injected immediately in the event of a severe, life-threatening reaction (anaphylaxis)

If you are diagnosed with a food allergy, follow your doctor's instructions . Consider seeing an allergist (a doctor who specializes in diagnosing and treating allergies).

Prevention

To reduce your chance of having a food allergy reaction:

  • Avoid eating or drinking substances to which you know you are allergic.
  • Be aware the food may become contaminated by shared utensils, containers, and during preparation.
  • Consider wearing a medical alert bracelet to inform others of your allergy.
  • If you go to a restaurant, discuss your allergy with the food server. Ask about all ingredients.
  • If you have a severe, anaphylactic-type food allergy, ask your doctor if you should carry a dose of epinephrine with you.
  • Learn the other names for all your allergens. This will help you recognize them on an ingredients list.
  • Read the ingredient label on every food product that you eat.

Last reviewed: September 2011 by Michael Wein, MD.

RESOURCES:
CANADIAN RESOURCES:
References:
  • Boyce JA, Assa'ad A, Burks AW, et al. Guidelines for the diagnosis and management of food allergy in the United States: summary of the NIAID-sponsored expert panel report. Nutr Res . 2011 Jan;31(1):61-75.
  • Dambro MR, Griffith JA. Griffith's 5-Minute Clinical Consult. Baltimore, MD: Lippincott, Williams, and Wilkins; 1999.
  • Food allergy: an overview. National Institute of Allergy and Infectious Diseases website. Available at: http://www3.niaid.nih.gov/topics/foodAllergy/PDF/foodallergy.pdf . Published July 2007. Accessed July 7, 2009.
  • Food Allergy and Anaphylaxis Network website. Available at: http://www.foodallergy.org . Accessed July 7, 2009.
  • Middleton E. Allergy: Principles and Practice. 5th ed. St. Louis, MO: Mosby-Year Book, Inc.; 1999.