Reasons unclear for rise in allergies

Posted on: Tue, 01/03/2006 - 10:58pm
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Reasons unclear for rise in allergies
One expert says the increase in American kids' reactions to foods is a "moving target" -
Tuesday, January 03, 2006
BRUCE TAYLOR SEEMAN Multiple-choice question: Why are more American kids allergic to foods, particularly peanuts?
The Oregonian
A) Their immune systems are confused by increasingly clean homes.

B) Nervous parents wait too long to feed their children peanuts.

C) We roast peanuts rather than boil them.

D) Maybe one of the above, and/or something else.

Unfortunately, the answer is "D."

But whatever biological mysteries are at work, U.S. children are more likely to be allergic to peanuts than kids in China, Israel and many underdeveloped nations, experts say.

One study estimates that American children's rate of allergy to peanuts and tree nuts (such as walnuts and pecans) -- about 1 percent of those under age 18 -- has doubled in recent years. No one can say why.

"It's a moving target," said Dr. Robert Wood, a pediatric immunology professor at Johns Hopkins University. "The numbers may be different by the time the next study gets done."

Deaths from allergic reactions to food are not officially counted, but studies suggest 150 to 200 fatalities a year, experts say. Case studies of 32 food-allergy deaths from 1994 through 1999 showed that most victims died of reactions to nuts, most had asthma, and 13 were under 18 years old.

Although rare, deaths from food allergies can occur with shocking caprice -- as in the recently reported case of a 15-year-old Canadian girl with a peanut allergy who died after kissing her boyfriend, who had just eaten a peanut-butter snack.

Studies of peanut, tree nut, fish and shellfish allergies suggest 11.4 million Americans, or about 4 percent of the population, have food allergies, according to the Food Allergy & Anaphylaxis Network ([url]http://www.foodallergy.com[/url]). Ten years ago, scientists believed less than 1 percent of the population was affected.

In 2003, about 1,800 children under 18 were hospitalized because of food allergies, according to a federal estimate. That number had increased only slightly during the preceding decade, but researchers say many allergic episodes go uncounted when hospitals misclassify them.

"The data are not clear enough to say what the true rate of increase has been, but we would be very comfortable saying the rate of food allergy has truly increased," Wood said.

The only treatment for a severe allergic reaction is a shot of epinephrine, a hormone that relaxes the airways of someone struggling with a life-threatening allergic response.

Government moves

to simplify label language On Jan. 1, a new federal law goes into effect requiring food manufacturers to use simple language -- milk instead of "caseinates," egg instead of "albumin" -- in food products' ingredients lists. The law will apply to peanuts, tree nuts, milk, eggs, fish, wheat, soybeans and crustaceans (such as shrimp and crab). Proteins in these foods cause about 90 percent of allergic reactions.

Meanwhile, some advocates are pushing for federal guidelines for schools to create emergency-action plans for allergic students.

In well-prepared schools, administrators have assembled teachers, parents, a school nurse and others to discuss how to handle emergencies and how to make a school safe, said Anne Munoz-Furlong, founder of the Food Allergy & Anaphylaxis Network, a group advocating more protections. "Nut-free" zones are becoming more common on school lunch tables.

Even highly sensitive peanut-allergic children are unlikely to experience a severe reaction from casual external contact with peanut butter, research has shown. Soap and water effectively remove the allergen from surfaces such as tabletops, while disposable wipes work well with hands.

But reactions do occur, most often when a child unknowingly eats something containing an allergen. Serious problems result when a school's files contain nothing from a child's doctor about a condition, what symptoms to look for, and how and when to give medication.

"A child eats something, thinks it was safe, but they have a reaction," Munoz-Furlong said. "They're sent to the office, the office staff calls the parents. Or the child has asthma, and they give her an inhaler. The reaction gets completely out of control, and when you bring epinephrine into the picture, it's too late."

An allergic reaction occurs when the body mistakenly identifies something as an invader and activates a portion of the immune system. People with hay fever, for example, overreact to the inhalation of pollen. The same process occurs in food allergies, with protein acting as the trigger.

In someone allergic to peanuts, for example, the body senses a specific protein has attached to cells in the body. To "protect" the cells, it sends out special antibodies called immunoglobulin E, or IgE. When IgE reaches the cells, it causes them to release histamines and other chemicals that may cause itching, nausea or restricted breathing.

"Hygiene hypothesis" links

allergies and cleanliness In trying to explain the increase in allergies, many scientists have embraced the "hygiene hypothesis." It holds that some people's immune systems have gone out of whack because America's increasing cleanliness has changed the behavior of IgE.

The central role of IgE is to help fight infections. But as America has become more sanitary, and as antibiotics have cut down on infections, IgE has less work to do, making it restless and prone to attack new things.

"The more (IgE) is left 'unbusy' because we're not being exposed to germs early in life, the more it could direct its attention toward allergies," Wood said.

Some data support this idea. Allergy rates are lower in many underdeveloped nations, perhaps because the immune systems of those who live there are constantly exercised.

But the hygiene hypothesis, which would apply to all kinds of allergies, doesn't explain everything.

"It's not clear that it's the whole story," said Dr. Marshall Plaut, chief of allergic mechanisms at the National Institute for Allergy and Infectious Diseases.

Doctors have successfully "desensitized" patients with allergies such as hay fever by injecting them with small but increasing doses of pollen. Such "immunotherapy" often causes severe reactions when tried against food allergies -- an effect scientists are trying to understand and avert.

Mindful of the hygiene hypothesis, researchers also are studying whether exposing children earlier in life to peanuts and other potential allergens may properly prepare their immune systems.

Peanut allergy rates in Israel are low compared with the United States, and some suspect that's because many Israeli children eat peanut snacks earlier and more often than American children do.

"It could be the hygiene hypothesis," Munoz-Furlong said. "It could be the way peanuts are processed. In China they boil them, and we roast them. Or, it could be how they introduce it; in this country, we wait until the third birthday. In Israel, it's typically before the first birthday."

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