“Food allergy is on the increase and we’re not really sure why,” Dr. Calhoun said. “There certainly is a hereditary component, but there’s also an environmental exposure component.”
Explore This IssueOctober 2010
Most allergies in children eventually go away. Dr. Calhoun pointed to research showing that egg allergies are resolved in 75 percent of cases by age seven, while milk allergies are resolved 76 percent of the time by age five. Wheat allergies are resolved 80 percent of the time by age five, and 20 percent of peanut allergies are resolved by age five.
Several of the presenters emphasized that accurately diagnosing a patient without using an FCT has been tricky because skin prick tests and in vitro tests are not very specific; only about 50 percent of those with positive results actually have allergies. But if the result is negative, there is a high probability that a patient does not have the allergy.
“Our goal, of course, is to improve our diagnostic ability so that we are able to correctly identify those patients affected by food allergies,” Dr. Veling said.
Although other tests being investigated include patch testing, this is not yet recommended because of insufficient evidence supporting its efficacy.
Non-standardized tests that have not been shown to be of value in the diagnosis of food allergy, according to Dr.
Veling’s review, include: Basophil activation, assays that measure activation markers on basophils; the measure of inflammatory markers in blood and feces to predict an allergic reaction; and IgE-positive cell count in the gastrointestinal tract or evaluation of gut mucosal responses to allergen instillation during endoscopy.
She said that intradermal skin testing is not recommended at this time because it is potentially dangerous and overly sensitive and has an unacceptable rate of false-positive reactions.
Work is also underway on methods to prevent food allergies and treat them once they’re found. A study in the United Kingdom, Learning Early About Peanut Allergy (LEAP) is looking at the effects that peanut products have in children who are considered to have a high risk of developing peanut allergies, said William Reisacher, MD, an assistant professor of otorhinolaryngology at Weill Cornell Medical College in New York City and director of the Allergy Center there.
The children, aged four to 10 months, already have eczema or an egg allergy, making them more likely to develop a peanut allergy; one group is fed a peanut snack three times a week, and another group is not. Rates of peanut allergies will be compared after five years.