Researchers from Stanford University examined 72 studies of food allergies, but noted that although there is much interest in food allergies, there is no clear consensus on the most effective diagnostic approaches. They also said there is no conclusive evidence to show that the prevalence of food allergies is increasing, but that they likely affect more than 1 to 2 percent of the population, but less than 10 percent.
One major problem, they found, is that it is difficult to diagnose food allergies, as there is no clear dividing line between ‘true’ allergy and food intolerance.
“The evidence for the prevalence and management of food allergy is greatly limited by a lack of uniformity for criteria for making a diagnosis,” they wrote, adding that overdiagnosis or misdiagnosis of food allergies also “serves to perpetuate some public misperceptions that food allergy is a trivial medical condition.”
Test limitations
They said that this lack of uniform criteria, as well as limited sensitivity of the most common allergy tests, such as the skin test and blood serum test, which looks for antibodies in the blood for certain foods, means that food allergies are overdiagnosed.
In fact, less than 50 percent of those with unclear symptoms who test positive for food allergies actually suffer from a food allergy, they wrote. And while avoiding certain foods may be less dangerous than risking a severe allergic reaction, the authors warn that inappropriate diagnosis could lead to unnecessary nutritional and social difficulties.
They wrote: “Patients with nonspecific symptoms (rash, abdominal complaints) who have positive SPT or serum food-specific IgE studies to foods have less than a 50% likelihood of actually having a food allergy (given the sensitivity, specificity, and prevalence).
“Inappropriately diagnosing such individuals with food allergy may unnecessarily subject them to broad dietary restrictions, the risk of nutritional problems from elimination diets (eg, milk or egg elimination in children), significant anxiety and worry, and the social challenges food allergies cause.”
The researchers concluded that more research in the form of randomized controlled trials is necessary to determine the effectiveness of food elimination diets for the treatment of non-anaphylactic allergies.
Source: Journal of the American Medical Association
2010; 303(18):1848-1856
“Diagnosing and Managing Common Food Allergies: A Systematic Review”
Authors: Jennifer Schneider Chafen; Sydne Newberry; Marc Riedl; Dena Bravata; Margaret Maglione; Marika Suttorp; Vandana Sundaram; Neil Paige; Ali Towfigh; Benjamin Hulley; Paul Shekelle