Food allergies are serious business -- just ask 18-year-old Dane of Charlotte, North Carolina. With milk, eggs, peanuts, shellfish, chicken, potatoes, and garlic -- and many other foods -- on his "do not eat" list, he suffers from true, life-threatening food allergies.
To avoid a trip to the emergency room, everything Dane eats must be made from scratch: "I don't eat in restaurants or from vending machines," he says, "[and] I try not to be around a lot of food, which makes it a little isolating because so much of our culture and socialization revolves around food."
But there are many allergy sufferers who practice the same devout food avoidance Dane does -- and don't actually have to, according to a paper published Wednesday in the Journal of the American Medical Association.
While a considerable percentage of Americans report that they have a food allergy, the true incidence of food allergies may be far less, says Dr. Marc Riedl, an author of the paper and an allergist and immunologist at the University of California, Los Angeles.
"If you look at the numbers, roughly half of the people who believe they have an allergy, do not," Riedl says.
Some of these misled patients are self-diagnosed, misinterpreting heartburn or food intolerance with a true allergy, he says. Others have seen doctors who have misinterpreted allergy test results and hence have been told to avoid foods that they don't actually have to.
Dane says he sees this in some of the families in his allergy support group.
"Some have mistakenly been told that a positive skin test means that their child is allergic," he says. "This is not the case."
This is one of the biggest take-home messages of Wednesday's paper, says Dr. Hugh Sampson, chief of pediatric allergy and immunology at New York's Mount Sinai School of Medicine: one positive allergy test result does not a food allergy make.
There is not a unified definition of what a food allergy is or how to test for it reliably, Riedl says, and this is why overdiagnosis occurs.
In an attempt to address the issue, the National Institute of Allergy and Infectious Diseases commissioned Riedl and his colleagues to review the research on food allergies from 1988 to 2009. The resulting paper will help a panel of experts write new guidelines on how to define, diagnose, and treat food allergies. The new guidelines are scheduled to be released by the end of June.
Prevalent over-diagnosis or mistaken self-diagnosis of food allergies is nothing new, says Dr. Wesley Burks, chief of the Division of Pediatric Allergy and Immunology at Duke University Medical Center.
The National Institute of Health has been wary of this issue since the early 1980s, Burks says, when a landmark study found that one third of families reported having someone in the family with a food allergy -- a prevalence that was grossly inconsistent with the one-percent incidence of food allergy seen at the time.
More recently, misuse and misinterpretation of diagnostic tests has become a major issue.
"One of the things we see often is that doctors order skin tests [where the food in question is exposed to a scratch in the skin and monitored for a reaction] and diagnose based solely on that," Sampson says. The problem is, as past research has shown, a positive skin test only translates into a true allergy 35 to 40 percent of the time, he says, leaving a lot of room for false positives.