Allergic reaction: Food allergies increasing, especially among children

Denise Bunning had no idea that switching her 6½-month-old son from breast milk to a milk-based formula would threaten his life. But Bryan's first sips proved perilous. His lips and tongue swelled, and his eyes rolled back. "I didn't know what was happening," says Bunning, who, with her husband, David, co-founded the Food Allergy Project in Chicago.

Bryan was diagnosed with life-threatening allergies to milk, eggs, tree nuts and sesame seeds. So when their second son, Daniel, was born, the Bunnings took precautions. Still, at 9 months he also had an anaphylactic reaction after a babysitter inadvertently put a milk-soiled bib around his neck. "His allergies are even worse," she says. "In addition to milk, eggs and tree nuts, he is also allergic to beef, turkey and shellfish."

For reasons scientists cannot yet explain, food allergies are increasing, especially among children. According to the Centers for Disease Control and Prevention, the number of food or digestive allergies in those younger than 18 increased 18% in the last decade. In an October 2008 report, the CDC estimated that 3 million U.S. children and teenagers have a food or digestive allergy, compared with just more than 2.3 million in 1997. And more than 9,000 annual pediatric hospital discharges had a food allergy diagnosis.

But the problem goes beyond children -- 1% to 2% of adults have food allergies, which can emerge at all ages for many reasons. Recent studies focus on pediatric patients, but many of the themes are applicable. The key differences involve patterns. For instance, the most common food allergies among adults are shellfish, fish, peanuts, tree nuts and eggs. For kids, it's cow's milk, eggs, peanuts, tree nuts and sesame seeds. Also, while children often outgrow these issues, adults do not.

"There's an epidemic of allergies," says Clifford Bassett, MD, assistant clinical professor of medicine at Long Island College Hospital in Brooklyn and medical director of Allergy and Asthma Care of New York. He also is the vice president of public education for the American Academy of Allergy, Asthma & Immunology. "Today, one in 26 children has a food allergy, up from one in 30 in 1997."

According to the CDC, eight foods -- milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat -- account for 90% of allergies. With reactions ranging from tingling around the mouth and lips to hives and even death, management can be challenging. "There are 200 fatalities each year from food allergies. This is an important problem," Dr. Bassett says. "There needs to be more education of physicians and patients. Parents need a plan, an EpiPen, and we need to teach them how to be label detectives."

The hardest part, says the Food Allergy Project's David Bunning, is unexpected exposure. It can be a bite of a cookie, peanut shell dust at a ballgame or a dairy-coated pill. But all can lead to an anaphylactic reaction or even death. "Avoidance becomes all-encompassing," he says. "And regardless of how careful we are, every year or so we have an accidental cross-contamination."

A little bit of dirt and other theories

Corresponding to this increase in food allergies is an increase in allergies overall, says David L. Rosenstreich, MD, director of the division of allergy and immunology at Montefiore Medical Center in New York. "There is clearly more asthma, there is clearly more rhinitis. Why is this happening?"

While possible explanations abound, not enough evidence exists to pinpoint a cause, says Jonathan Field, MD, director of the pediatric allergies and asthma clinic at New York University's Langone Medical Center, in Bellevue.

Food-specific theories question if our diets have changed in subtle ways, maybe with nutrients that push more toward allergic responses. Others note that eating more or maybe even less of specific allergenic foods is to blame. Some theories even center on how a food is processed. For example, maybe roasting peanuts makes them more allergenic than boiling or frying, a common preparation in Asia, where peanuts are frequently eaten but peanut allergy rates appear lower, says Scott H. Sicherer, MD. He is associate professor of pediatrics at the Jaffe Food Allergy Institute, Mount Sinai School of Medicine in New York. Other theories blame a lack of sun exposure and decreased vitamin D, he adds, noting data indicating that more people with anaphylaxis live in northern climates.

The hygiene theory also is popular. Some experts say society is too clean, keeping kids' immune systems from maturing as they did in the past. "The hygiene hypothesis says that we are oversanitizing the early environment of the child," Dr. Bassett says. "The immune system has less exposure to dirt, germs and bugs."

In support of this perspective, researchers point to Eastern Germany before the fall of the Berlin Wall. "They had much lower rates of allergy," Dr. Field says. "As they were westernized, they had more."

Maybe a little dirt is not so bad, Dr. Rosenstreich says. "In the farm studies, children who live on farms in close proximity to animals and are exposed to endotoxins have fewer allergies. And it looks like a pet in the home in the first year of life may well protect children from asthma. This is the opposite of what we've been teaching."

According to a release by the American Academy of Allergy, Asthma & Immunology, new research casts doubt on food avoidance recommendations -- specifically, that infants and new mothers avoid eating peanuts. The study, published in the November 2008 Journal of Allergy and Clinical Immunology, found that children who avoided peanuts in infancy and early childhood were 10 times as likely to develop peanut allergy as those who were exposed to them.

Researchers measured the incidence of peanut allergy in 8,600 Jewish school-age children in the United Kingdom and Israel. Prevalence of the allergy in the U.K. was estimated at 1.85% versus 0.17% in Israel. "Actually, peanut is eaten at an earlier age in Israel, lending argument to the idea that perhaps earlier exposure is not a problem," Dr. Sicherer says.

Nonetheless, the AAAAI cautions that, although the results are promising, they shouldn't translate to changes in treatment just yet. "While this study's findings provide optimism for prevention of peanut allergy in the future, randomized, controlled trials are needed to verify that early introduction of peanut is indeed effective," says Jacqueline A. Pongracic, MD, vice chair of the allergy academy's Adverse Reactions to Foods Committee.

Similarly, a study published in the Oct. 28, 2008, Journal of Allergy and Clinical Immunology explored milk exposure and milk allergies. Investigators from Johns Hopkins Children's Center and Duke University found that giving children increasingly higher doses of milk over time may ease milk allergy. "They were able to greatly increase tolerance to milk," Dr. Rosenstreich says. "Total avoidance may also be a mistake."

In another twist, a recent study found evidence that early cat ownership may help protect young children against developing asthma symptoms. The research was conducted by scientists at the Columbia Center for Children's Environmental Health at Columbia's Mailman School of Public Health, in New York.

Education and research

Clinical signs of food allergy often are confused with other reactions, most commonly intolerance. "The question is are they truly food allergic," says Jonathan Bernstein, MD, professor of medicine in the division of immunology and allergy, Dept. of Internal Medicine at the University of Cincinnati College of Medicine.

Guidelines published in the March 2007 Annals of Allergy, Asthma & Immunology help clarify food allergy diagnosis and management, which begin with a detailed history, confirmatory testing and education about day-to-day living. The diagnostic gold standard is the double-blind, placebo-controlled food challenge. "For children, many food allergies are outgrown, so repeated evaluations are needed," Dr. Sicherer says.

In a study in the September 2008 BMC Medical Education, however, researchers found that primary care physicians are not trained adequately in food allergy management. This survey and others found a majority of respondents were unable to identify risk factors for anaphylaxis.

"Our previous studies also showed that too many doctors did not know, for example, exactly how to teach people how and when to use self-injectable epinephrine," Dr. Sicherer says. "We were funded by the U.S. Dept. of Agriculture to create an educational program for doctors who care for teenagers and adults with food allergy. The program focuses on nuances. ... There are a lot of things the doctor must keep up on, including new labeling laws, for example."

Dr. Bernstein says it's important for primary care physicians to ask patients what happens when they eat the suspected food. "We don't want to create hysteria," he says. "It's important to find out if it is an allergy, and sending someone for a consult to clarify is not bailing from your patient."