by Amy Spangler
July 08, 2010

Pass the peanuts may soon be passé if opponents of peanuts on airplanes have their way. The Department of Transportation (DOT) is considering banning peanuts on airplanes, and has given the public until August 6, 2010 to comment on the ban. But the DOT cautions that without scientific proof of severe allergic reactions to the tiny peanut particles that might be present on a plane, it cannot implement a ban.

Although peanut allergy is thought to be among the most serious food allergies, the overall prevalence of food allergies is unclear—so too are strategies for their diagnosis and management. The National Institute of Allergy and Infectious Disease (NIAID) is in the process of developing clinical practice guidelines to ensure better diagnosis and treatment of food allergies. To assist in that effort, researchers conducted a systematic review of the existing scientific evidence.

More than 12,000 articles were identified but only 72 met the criteria for inclusion—sufficient data and rigorous testing—revealing that most of the studies on food allergies were poorly done making the results suspect. While nearly 30 percent of the population report having a food allergy, only about 8 percent of children and 5 percent of adults actually do, according to Dr. Marc Riedl, one of the study’s authors. “Even the belief that breastfed babies have fewer allergies or that babies should avoid eggs in their first year of life lack strong evidence,” said Riedl.

Studies rife with limitations
The authors cited numerous study limitations—food allergy has no universally accepted definition; self-report was used as a means of diagnosis; no well-accepted criteria for diagnosing food allergies; limited data for the effectiveness of various treatments such as elimination diets, immunotherapy (shots), probiotics, and education; and limited data for the use of prevention strategies such as exclusive breastfeeding, delayed introduction of solid foods, use of hydrolyzed formulas, and use of probiotics.

Although U.S. studies found a statistically significant increase in food allergy over time (3.3 percent of children in 1997 compared to 3.9 percent in 2007), the authors of those studies acknowledged that the increase could be due to increased awareness rather than an increase in actual food allergies.

The authors concluded:

• Food allergies affect 1-2 percent but less than 10 percent of the population;
• It is unclear whether the prevalence of food allergies in increasing;
• No one diagnostic test has sufficient sensitivity to be recommended over other tests;
• No single test (either the skin-prick test or IgE antibody test) should be used as the basis for a diagnosis of food allergy;
• A food challenge test is a better way to confirm a diagnosis of food allergy;
• Elimination diets are the mainstay of allergy therapy. However, their effectiveness is unproven;
• Immunotherapy may result in desensitization, but long-term tolerance is yet to be determined; and
• Definitions of ‘high-risk’ and ‘hydrolyzed formula’ do not exist. Therefore the effectiveness of probiotics in conjunction with breastfeeding or hypoallergenic formula in preventing food allergy in high-risk infants is unclear.

Data on food allergies is plentiful, but very little is high quality. Before decisions can be made about prevalence, treatment, and prevention, consensus needs to be reached as to the criteria for food allergy and evidence-based guidelines for making the diagnosis. If you have a family history of food allergy, talk with your doctor and your baby’s doctor before pursuing any strategies to prevent food allergies—the unproven benefits may not be worth the known risks.