May 12, 2010 -- 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.
Fact or Fiction: Clearing Up the Allergy Myths
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.
Burks says that often a child will come into his clinic with a long list of foods they supposedly can't eat, but it's actually only a couple of foods that are actually causing the reaction. Other times, the symptoms are only mild and vague, such as a headache, and don't point to a clear allergy, but their doctors have diagnosed it as such.
"There just isn't a good understanding in the medical community of how to use these tests. That's why they are doing these guidelines," he says.
The Dangers of Over-Diagnosis
While mistakenly avoiding a food you can eat is certainly less dangerous than accidentally eating something that will send you to the hospital, there are some serious repercussions to this trend of over-diagnosis, Riedl says.
For the individual patient with a misdiagnosis, they can be put on very restrictive diets that can cause a lot of stress and anxiety, he says, and occasional nutritional problems.
"I spend a lot of time educating people on what constitutes a real allergy and what level of concern they need to have" because patients come in thinking they are more allergic than they are, Riedl says. "It's very important that they're not worried about having a life-threatening problem when that's not the case."
On a more public health level, over-diagnosis "leads to some trivialization of this condition," Riedl says, "and people start to associate food allergy with dislike of a food or mild intolerance," which makes people take true food allergies less seriously.
Dane agrees, saying that this type of colloquial use of the term "allergic" is annoying because "it diminishes the seriousness of the situation that people with allergies live with day in and day out."
Putting Allergy Tests to the Test
How do you know your food allergy is for real?
The two main allergy tests, the skin test, and a blood serum test -- which looks for antibodies in the blood for specific foods -- are not conclusive on their own, Sampson says.
"The tests are good for telling us if someone has antibodies for a food, not so good for telling us if someone will have a reaction to the food," he says. "The more antibodies you have, the higher the likelihood of an allergic reaction, but even that's not full proof," he adds.
So if you've been diagnosed as allergic after one of those tests, but you haven't had an allergic reaction to that food in the past, it's likely that you are not actually allergic, Sampson says.
The "gold standard" of allergy testing is something called an oral food challenge, Riedl says, in which small amounts of the food in question are disguised and given to the patient while they are under observation. This is best done if the patient doesn't know if they are actually getting the food so they don't anticipate a reaction.
Unfortunately, this type of test is time-consuming, so many doctors are reluctant to do it, Riedl says.
The Future of Food Allergies
Short of the food challenge, antibody levels and a past history of reactions, when interpreted by an experienced professional, are the best way to work through what is a food allergy and what is just a food aversion, or a bad case of indigestion.
With the help of the National Institute of Allergy and Infectious Diseases project on this topic, allergists hope that a clearer understanding of diagnosis and management of food allergies can be found.
"The amount of information we have now is very limited," Sampson says. "My hope for this article, and these guidelines, is that people who have control of funding will realize the need to put money into research on this. That would be a tremendous service."