Food allergies can be caused by a wide variety of foods, although the most common are cow's milk, hen's eggs, peanuts, tree nuts, fish and shellfish. Food allergies can cause many types of symptoms, from mild rashes to life-threatening anaphylaxis.
While about two percent of Americans are believed to be affected by food allergies, researchers have found there is no single method that has been shown to be the best way to diagnose the condition. A combination of clinical history and one of several tests, such as a skin prick test, are commonly used by physicians to diagnose food allergies.
The new study found that variation in the measures used to make the diagnosis is limiting advancements in how to best treat patients with the condition. The first critical look at the scientific literature published about food allergies was conducted by The Southern California Evidence-Based Practice Center based at the RAND Corporation and the VA Greater Los Angeles Healthcare System.
Although there have been some reports suggesting food allergies are increasing, the lack of high-quality research on the condition makes it impossible at this time to determine whether the incidence of food allergies is actually rising, according to researchers.
While the standard treatment for food allergies is to remove the suspected problem food from a person's diet, researchers say they found little research that establishes the validity of that approach. Testing the approach among people with potentially life-threatening allergies would be unethical, but such studies should be considered for people with lesser symptoms, such as skin rashes, in order to establish the net effect of potential benefits compared to potential harms, according to researchers.
"While there have been gains in our understanding of how to diagnose and manage people with food allergies, the lack of standardized criteria for diagnosis makes it difficult to compare management strategies across studies and limits our ability to determine best practices for the condition," said senior author Dr. Paul Shekelle of the Greater Los Angeles VA Healthcare System and the RAND Corporation, a nonprofit research organization.
The lack of uniformity also raises the potential for over diagnosis of the problem, which means that some people may be unnecessarily limiting their diets, according to the study.
"What's needed now to advance the field are guidelines for how to diagnose food allergies, so that future studies will be comparable, and patients and providers can have confidence in the diagnosis," said lead author Dr. Jennifer J. Schneider Chaffen, a fellow at the Center for Primary Care and Outcomes Research at Stanford University and the VA Palo Alto Healthcare System.
More research is also needed to better understand promising treatment approaches such as immunotherapy and several approaches that may help prevent the development of food allergies in high-risk infants, according to the study.
Researchers compiled their findings by reviewing the available medical evidence published between 1988 and 2009 on the prevalence, diagnosis, management and prevention of food allergies. They focused on studies examining allergies to cow's milk, hen's eggs, peanuts, tree nuts, fish and shellfish—foods that account for more than half of all food allergies.
Study abstract: http://www.rand.org/health/abstracts/2010/shekelle.html
Rand Health Research: http://www.rand.org/health/