Nov. 28, 2005 -- An increasing number of children have developed allergies to peanuts and other common foods, and finding the cause for this rise has doctors going nuts.
The death Monday of a Canadian teenager who kissed her boyfriend after he had eaten a peanut butter snack underscores the severity of this growing problem.
"The frequency of people dying from peanut allergies is not all that high, but when it does happen, it certainly is tragic," said Dr. Miles Weinberger, director of the Pediatric Allergy and Pulmonary Division of the University of Iowa Department of Pediatrics.
According to the American Academy of Allergy Asthma and Immunology, peanut allergies in children increased twofold from 1997 to 2002. Some studies suggest about four percent of the U.S. population -- more than 11 million people -- have food allergies. Ten years ago, that figure was believed to be only one percent.
But some researchers say an increasing awareness is causing a spike in reports of allergies. Other scientists believe the reason for the increase lies in the way peanuts are prepared. Still others believe children are exposed to too few allergens in their youth. Who's right?
Boiling Versus Roasting
Most peanuts in the United States are dry-roasted at high temperatures. It is the high roasting temperatures, some believe, that causes problems by changing the protein structure. "The dry-roasting process makes these peanuts more allergenic," Weinberger said.
A report in the June 2001 Journal of Allergy and Clinical Immunology found that frying or boiling peanuts, as practiced in China, appeared to reduce the allergenicity of peanuts compared with dry roasting. According to the study's authors, this may explain the different rates of peanut allergy seen in the United States and China.
"Asians predominantly eat boiled peanuts," Weinberger said. "Asians have a much lower incidence of peanut allergies."
Are Kids Today Too Clean?
A growing body of research finds that children raised in clean, urban settings are more likely to develop allergies than children raised in rural areas or farming communities.
The "hygiene hypothesis" holds that children exposed to allergens and microbes at an early age develop a greater tolerance for those allergens, and are therefore less likely to suffer from asthma or allergies.
Are "hygienic" environments to blame for a rise in food allergies?
"The most likely explanation is [the] hygiene hypothesis," said Dr. Donald Leung, an allergy specialist at National Jewish Medical and Research Center in Denver.
But Weinberger says the hygiene hypothesis is questionable. "At this point, it's generally regarded as intriguing but controversial. For every example, you can find other examples where it's not so."
And proponents of this hypothesis risk ignoring an important point: "Infections used to kill many more people than allergies," said Dr. Amal Assa'ad, professor and clinical director of the allergy and immunology division at the Cincinnati Children's Hospital Medical Center.
Allergy Awareness May Be Driving Statistics Upward
Parents and doctors alike are increasingly aware of asthma and allergies. But is this awareness fueling the statistical increase in reported allergies more than any actual increase in allergies?
"There is no clear evidence for the increase in number of children allergic to peanuts other than the above mentioned study," said Assa'ad, referring to the AAAAI study. "There is definitely increased awareness."
Assa'ad believes news coverage may be partly responsible for the rise in reported cases of allergies. "Anytime there's more media coverage, then there is increased awareness," she said.
As in many aspects of allergy research, there are differing points of view.
"We are seeing a great deal of food allergy," Weinberger said. "But I can't tell if it represents a large increase, or if this is simply more referrals because of our interest and expertise with regard to food allergy."