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What is a food allergy?

A food allergy is an abnormal response to a certain food. If your child has a food allergy, exposure to that food causes an immune system response, leading to symptoms that range from uncomfortable to life-threatening. Often, an allergic reaction will occur the second time your child is exposed to a particular food. However, in some cases, your child could be sensitized to a food through breast milk.

Ninety percent of food allergies are caused by the following six foods: milk, eggs, wheat, soy, tree nuts, and peanuts. Eight percent of children under age 6 have food allergies.

Food Allergy | Symptoms & Causes

What are the symptoms of a food allergy?

Symptoms may begin anywhere from a few minutes to an hour after your child ingests the food. Common symptoms include:

  • vomiting
  • diarrhea
  • cramps
  • hives
  • swelling or rash
  • eczema
  • itching or swelling of the lips, tongue, or mouth
  • itching or tightness in the throat
  • difficulty breathing
  • wheezing
  • lowered blood pressure

The symptoms can be different for milk allergies and soy allergies, which are often seen in infants and young children. The symptoms may include:

If a milk allergy is suspected, your doctor may change your baby’s formula to a soy formula. If your baby has problems with soy formula, your child’s physician may suggest a hypoallergenic formula.

Many children do outgrow their allergies, but allergies to peanuts, tree nuts, fish, and shellfish may last a lifetime.

What causes food allergies?

A food allergy occurs when the body's immune system identifies a food as harmful, triggering an allergic reaction. According to the National Institute of Allergy and Infectious Diseases, even a small amount of the food can cause a severe reaction in a highly allergic child.

Food Allergy | Diagnosis & Treatments

How is a food allergy diagnosed?

The first step to diagnosing a food allergy is a complete medical history. The allergist will perform a physical exam and ask questions about your child's symptoms to see if they are related to a food allergy. The allergist may do a series of tests to help identify a food allergy. The results will be reviewed along with your child's medical history to provide a diagnosis.

To help diagnose a food allergy, your allergist may recommend:

  • completing a food diary of all the foods your child eats each day
  • a skin-prick test
  • trying an elimination diet to cut certain foods from the diet, then slowly adding them back in one at a time to try to pinpoint the allergy
  • a blood test

How are food allergies treated?

There is no medication to prevent a food allergy. The best way to avoid an allergic reaction is for your child to avoid the foods that cause the allergy. If you are breastfeeding, you must also avoid those foods. In some cases, your allergist may have you introduce a food back into your child’s diet after a few months, to see if they have outgrown the allergy.

If your child’s allergy is severe, the allergist may prescribe an emergency kit that contains epinephrine. This is a medicine that immediately stops the symptoms of a life-threatening reaction.

How we care for food allergies

At Boston Children’s Hospital, our allergists provide diagnostic evaluations for food allergies that are supported by our advanced allergy testing facilities. Once an allergy is diagnosed, our allergists create an individual treatment plan for each child. Treatment may include education, medical management, and coordinated care with your child’s primary physician.

Food Allergy | Programs & Services