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Food Allergies

What are food allergies?

A food allergy is a reaction of the body's immune system to a certain food. Food allergies tend to be overdiagnosed, but about 5% of children have true allergic reactions to food. Your child may have a food allergy if he or she develops allergic symptoms within 2 hours after eating certain foods.

What are the symptoms?

  • Lips, tongue, or mouth swelling or itching
  • Stomach cramps, diarrhea, or vomiting
  • Hives and swelling beneath the skin
  • Itchy red skin (especially if a child already has eczema)

Some less common symptoms are:

  • Sore throat or throat clearing
  • Coughing
  • Nasal congestion, runny nose, sneezing, or sniffing (especially if a child also has hay fever)

Anaphylaxis (severe allergic reaction)

Some children have a severe allergic reaction (called an "anaphylactic reaction") that may be life-threatening. The symptoms of a severe reaction generally occur within minutes to 2 hours after contact with the food causing the reaction. Symptoms of such a reaction are a sudden trouble breathing, sudden trouble swallowing, weakness from a sudden fall in blood pressure (shock), or confused thinking. Any food-induced asthma attack or croup is anaphylaxis until proven otherwise.

What is the cause?

Allergic children produce antibodies against certain foods. When the child eats or drinks the allergic food, these antibodies come in contact with the food and start the allergic reaction. This reaction releases chemicals (such as histamines) that cause the allergy symptoms.

The tendency to be allergic is inherited. If one parent has allergies, each child has about a 40% chance of developing allergies. If both parents have allergies, the chance of food allergy rises to about 75% for each child. Often a child is allergic to the same food(s) as the parent or siblings.

Children who have other allergic conditions, such as eczema, asthma, or hay fever are more likely to have food allergies than children who do not have other allergies. A few children who have asthma, migraine headaches, colic, or recurrent abdominal pain may have attacks of these problems triggered by food allergies. If an attack is triggered by a food allergy the child will also have some of the common symptoms of food allergies listed above. Attention deficit disorder and behavioral disorders have not been scientifically linked to food allergies.

What are the most common food allergies?

Overall, the food that most often causes allergies is the peanut. In babies, allergies to eggs and milk products are more common. Peanuts (and peanut butter), eggs, cow's milk products, soybeans (and soy formula), and wheat cause over 80% of food reactions. These foods plus fish, shellfish (such as shrimp), and tree nuts cause over 95% of all food reactions. Chocolate, strawberries, corn, and tomatoes are often blamed for allergic reactions, but actually these foods rarely cause allergic reactions.

Will my child outgrow a food allergy?

At least half of the children who develop a food allergy during the first year of life outgrow it by the time they are 2 or 3 years old. Some reactions to food (for example, milk or soy) are more often outgrown than others. Although 3% to 4% of all babies have a cow's milk allergy, less than 1% of them are allergic to milk for the rest of their lives. Allergies to tree nuts, peanuts, fish, and shellfish (shrimp, crab, and lobster) often do last a lifetime.

How is it diagnosed?

The following steps may help you determine whether your child has a food allergy and what foods cause the allergy.

  1. Keep a diary of symptoms and recently eaten foods.

    If you already know what food is causing an allergic reaction, go directly to step 2. Otherwise, be a good detective and keep a diary of foods and symptoms for 2 weeks. Any time your child has symptoms, write down the foods that he or she ate during the last meal.

    After 2 weeks, look at the diary to see if your child ate any of the same foods on the days he or she had symptoms. Symptoms may depend on how much of the food your child ate. Anaphylactic reactions can be triggered by even small amounts of foods, but other allergic symptoms (for example, diarrhea) and their degree of severity usually depend on how much of the food your child eats.

    Reactions to food may be worse when a child is also reacting to other substances in the environment, such as pollens (hay fever). Therefore, food allergies may flare up during pollen season.

  2. Have your child stop eating the suspected food for 2 weeks.

    Record in the diary any symptoms that your child has during this time. If you have eliminated the correct food from the diet, your child should stop having allergic symptoms. Most children improve within 2 days. Almost all of them improve after 1 week of not eating the food causing the allergy.

  3. Have your child start eating the suspected food again. (CAUTION: Never do this if your child has had a severe or anaphylactic reaction to a food).

    This is called "rechallenging" and the purpose is to prove that the suspected food is definitely the cause of your child's symptoms. Give your child a small amount of the food you think is causing the allergy. The same allergic symptoms should appear within 10 minutes to 2 hours after the food is eaten. Call your child's healthcare provider before you rechallenge.

  4. Tests

    Skin prick tests or a blood test may also be used by your child’s doctor or allergist to help figure out what food your child is allergic to. The tests are especially helpful for severe food reactions.

How is it treated?

  • Avoid eating the food that causes the allergy.

    This should keep your child free of symptoms. If your child is breast-feeding and is allergic to a food that you are eating, do not eat this food until your child stops breast-feeding. Food allergens can be absorbed from your diet and enter the breast milk. Talk to a nutritionist if you have questions.

  • If hives or itching are the only symptoms, give Benadryl 4 times a day until the hives are gone for 12 hours.
  • Join the Food Allergy and Anaphylaxis Network.

    This national organization can help with any food allergy questions you might have. Contact them at 800-929-4040 or http://www.foodallergy.org.

  • Provide a substitute for any missing vitamins or minerals.

    Eliminating single foods from the diet usually does not cause any nutrition problems. However, if you eliminate a major food group, you will need to make sure your child gets all the nutrients he or she needs from other sources. For example, if you eliminate dairy products, your child will need to get calcium and vitamin D from other foods or supplements. Talk to your healthcare provider or a nutritionist about dietary supplements (such as vitamins).

  • Epinephrine

    If your child has a severe allergic reaction, you need to carry injectable epinephrine with you at all times. Keep epinephrine at home and school. Make sure that child care providers and school staff know that your child has a severe food allergy, and what to do if he or she has a reaction.

How can I help prevent food allergies?

Exclusive breastfeeding during the early months is helpful in preventing atopic dermatitis (eczema). Restricting the mother’s diet, however, has not been shown to be helpful. Recent studies have shown that delaying the introduction of high risk foods (such as eggs, fish or peanut butter) does not reduce the risk of becoming allergic to that food. Some studies have even shown that early introduction of high risk foods before a year of age actually reduces the rate of food allergies. For now, do not introduce baby foods before 4 months of age. After 4 months of age, however, there is no proven benefit from restricting any strained foods.

When should I call my child's healthcare provider?

Call 911 IMMEDIATELY if:

  • Your child develops any serious symptoms, such as wheezing, croupy, barky cough, trouble breathing, passing out, or tightness in the chest or throat.

Call during office hours if:

  • You suspect your child has a food allergy.
  • You want to rechallenge your child with a food you think your child is allergic to.
  • You have other questions or concerns.
Written by Barton D. Schmitt, MD, author of “My Child Is Sick,” American Academy of Pediatrics Books.
Pediatric Advisor 2013.2 published by RelayHealth.
Last modified: 2012-08-20
Last reviewed: 2012-05-14
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2013 RelayHealth and/or its affiliates. All rights reserved.
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