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Outgrowing allergies and when to get retested

Bryn Mawr Hospital November 2, 2017 General Wellness By Michele Columbo, MD

Q: I have a 12-year-old son who was diagnosed with a peanut allergy as a baby because of a severe reaction to peanut butter. He doesn’t have other allergies (that we know of) but we’ve never had him tested further. Do kids outgrow allergies? And when should they get retested for food allergies they were diagnosed with when they were little?

Certain allergies present mainly during childhood, such as wheat, egg, and milk allergies, and are very frequently “outgrown.” Allergies to shellfish, tree nuts and peanuts tend to be lifelong allergies—yet 20 percent of children with a peanut allergy will outgrow it. It would be reasonable to test children for food allergies every three to five years to find out if they have outgrown the allergy or are still allergic.

A food allergy skin test can be performed for most foods, including: 

  • Milk
  • Egg
  • Peanut
  • Soy
  • Wheat
  • Shellfish
  • Fish
  • Tree nuts (e.g., almond, cashew)

When this test is done correctly, a negative result (meaning no reaction/response) means that the chance of an allergic reaction to a food included in the above list is very small. A confirmative allergy blood test called RAST may also be ordered. In the case of some common foods, the allergy blood test can indicate whether the patient can eat the food in question and likely not react to it—even if the allergy blood test is positive for that food.

Food allergies vs. food sensitivity and the importance of food allergy testing

It is not uncommon for children and adults to be misdiagnosed with a food allergy. A child may have different symptoms related to having eaten something and the concerned parents or caregivers may believe that is a food allergy. In other cases, a patient may undergo allergy skin tests or blood tests, and these tests may produce “false positives.” In other words, food allergy tests may suggest that a patient is allergic to a food when in fact there is no allergy.

An example of this is with certain fresh fruits and nuts. When patients are strongly allergic to certain pollen such as birch and ragweed, they may experience itchy mouth and throat when eating certain fruits and nuts. These reactions are not real food allergies and are called oral allergy syndrome or pollen food syndrome. They can be uncomfortable, but they very seldom develop into true food allergies. Patients who have oral allergy syndrome may frequently have positive allergy tests for certain fresh fruits and nuts, but they are not at risk for severe allergic reactions such as anaphylaxis. It is important to consult with an allergy and immunology specialist who can review the patient’s medical history, particularly in reference to reactions to different foods. This specialist can perform and/or order appropriate allergy testing and interpret the results. An allergist can also supervise an oral food challenge when this is indicated.

Oral food challenges involve giving the patient a minute amount (about the size of a crumb) of the food in question, then waiting 20 minutes to see if there is a reaction. If there is no reaction, the food amount is doubled every 20 minutes. If the patient has no reaction to the highest dose of the food during an oral food challenge, it means that the patient is not allergic to that food. If the patient experiences an allergic reaction during the food challenge, the allergy and immunology specialist will administer appropriate medications to stop the reaction.

It is not uncommon for people to be diagnosed with food allergies when in fact they have a different disorder or condition, such as celiac disease or lactose intolerance. These conditions can produce gastrointestinal symptoms that can be thought to be allergic. Consulting an allergist can determine if a food allergy is present and verify previous allergy tests that might have been incorrectly performed and/or interpreted. Allergy evaluation and testing may also allow patients to reintroduce into their diets foods they were told they were allergic to.

As we head into the holiday season and a wide variety of foods your child may have been told not to eat, consider seeing an allergy and immunology specialist for evaluation and retesting—and to have peace of mind either way.