According to Children’s National Director of the Food Allergy Program, Hemant Prashad Sharma, M.D, about 1 in 13 kids have a food allergy. A food allergy is an adverse reaction to a specific food that the body thinks is harmful, according to the Centers for Disease Control and Prevention (CDC). The immune system in someone with food allergy produces immunoglobulin E (IgE), an antibody, to fight the food allergen. As a result, when the person is exposed to that food, IgE binds to it and causes the release of a number of chemicals, including histamine. This leads to an allergic reaction.

Some common food allergens include:

  • Cow’s milk
  • Eggs
  • Peanuts
  • Tree nuts (walnuts, pecans, hazelnuts, almonds, cashews, pistachios, and macadamia nuts)
  • Fish
  • Shellfish
  • Soybeans
  • Wheat

Common food allergy symptoms include:

  • Skin and mucous membranes:
    • Hives, redness, and swelling of the face or extremities
    • Itching and swelling of the tongue, lips, mouth and throat
  • Gastrointestinal tract:
    • Nausea, abdominal pain, vomiting and diarrhea
  • Respiratory system:
    • Runny nose, sneezing, coughing, wheezing and shortness of breath
  • Cardiovascular system:
    • Hypotension (low blood pressure), dizziness and syncope (fainting)

Any of these food allergies can lead to a severe, life-threatening reaction called anaphylaxis. It is estimated that food-induced anaphylaxis is the reason for about 200,000 emergency department visits each year.

Testing for food allergies
Food allergies, however, are a manageable conditions and can be diagnosed even in infancy. Some tests for food allergies include:

  • Skin tests: A skin prick test is usually done on the back or forearm. A small amount of the allergen is introduced on the skin surface, and the skin is pricked. After 15 minutes, it is noted whether or not a wheal, which is a small reddish bump, is formed. If no wheal appears, it is usually considered a negative skin test. If a wheal appears, it is considered a positive skin test.
  • Blood tests: Another test that may be performed is a blood test known as a radioallergosorbent test (RAST). RASTs check the IgE antibody levels in the blood for certain food allergens. While both of these tests are very good diagnostic tools, neither is 100 percent accurate and false positives and negatives are possible. The only definitive test for a food allergy involves seeing what happens after the suspect food is eaten.
  • Food challenge: If the other tests are not conclusive, a food challenge may be recommended by your allergist. This involves eating gradually increasing amounts of the suspect food in a medical setting, and observing for any signs of an allergic reaction.
  • Elimination diet: During an elimination diet, suspect foods are removed from the diet for a few weeks. If the symptoms cease during this time, it is likely that this food is causing the symptoms. The food is then gradually reintroduced to the diet. If the symptoms return, it can be concluded that the child is allergic to that food.

Dr. Sharma suggests that for the most accurate results, parents must be aware of their child’s history or the suspected food allergy to help guide the testing.

How to treat food allergies
The best treatment of food allergies is to stay away from foods and drinks that contain the allergen. It is important to read all of the labels on food packages and be wary of cross-contact of foods. Your child’s doctor will prescribe epinephrine autoinjectors for treatment of severe anaphylactic reactions.

According to Dr. Sharma, about 80-90 percent of kids allergic to milk, wheat, eggs and soy may grow out of their allergy, but the likelihood of outgrowing a peanut, tree nut or seafood allergy is only 10 percent.

ABOUT THE AUTHOR

Hemant Sharma, MD, MHS, is the Clinical Chief of the Division of Allergy and Immunology at Children’s National Health System in Washington, DC. He is Director of the Food Allergy Program at Children’s National, as well as Site Director for the National Institutes of Health Allergy and Immunology Fellowship Program.

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