National Jewish - Clean homes tied to asthma

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http://www.denverpost.com/Stories/0,1002,53%257E441941,00.html

Clean homes tied to asthma

Germs may boost kids' immunity, Denver team says

By Auge

Denver Post Medical Writer

Tuesday, March 05, 2002 - Researchers have identified yet another

problem you can blame on Mom: asthma.

But only if she was a meticulous housekeeper.

The theory that cleanliness might be connected to this country's soaring

rates of childhood asthma has been batted around for years. And a lot

of doctors and scientists dismissed it as nonsense.

But recently, researchers at Denver's National Jewish Research &

Medical Center have begun to bolster the so-called hygiene hypothesis

with evidence and explanation.

" Actually, it's not tidiness, but germ exposure " that may play a role in

whether or not a child develops asthma, Dr. Andy Liu of National Jewish

said.

If children don't get bacterial infections when they're young, their

immune systems may later overreact to dust or pet dander or other

causes of allergies that often lead to asthma, Liu said.

Liu and his colleagues started with data showing that children who grow

up in farming communities and developing countries are " one-third to 50-

fold less likely to develop allergy and asthma " than kids who live in

urban areas.

In a study in India, Liu and colleagues found that, as expected, kids in a

rural village were far less likely to have allergy symptoms than were kids

in an urban area 25 miles away. But they also found that those rural

homes had a lot more bacteria residue called " endotoxins, " which are

often left by animals.

Those endotoxins produce the infections that Liu believes may help

build immunity to allergy and asthma.

Monday, Liu led a symposium on the hygiene hypothesis among some

of the nation's top allergy and asthma specialists, assembled in New

York for the annual meeting of the American Academy of Allergy,

Asthma and Immunology.

Dr. Honsinger, a Santa Fe, N.M., allergist and academy board

member, said he thinks that there may be something to the hygiene

hypothesis.

" We have his (Liu's) data, and there's data from day care centers in

Arizona that showed kids weren't getting as many allergies in day care, "

he said. " They found kids have more respiratory infections, but not as

much allergy or asthma. "

Honsinger pointed out that new studies also indicate that children born

into households where dogs and cats already live are less likely to

develop pet allergies later on.

Already, other researchers and private companies are at work on

products that might put the hypothesis to work treating allergies and

asthma, Liu said.

" It's interesting to see how it's gained steam, " Liu said. " For years, I

would give talks and (ask) how many believe this, and nobody would

raise their hand. That's starting to change. "

" In the next five or 10 years, we'll probably know much better whether

this can lead us to a new generation of allergy and asthma treatment, "

Liu said.

Another, unrelated study presented at the conference may offer further

encouragement to the housecleaning aversion.

Researchers in England found that exposure to cat allergens was more

than three times higher while a room was being vacuumed than when

the cat dander was just lying around on rugs.

Still, not everyone is ready to toss their vacuum and buy a couple of

farm animals.

" I'm not sure there's enough evidence to point one way or another, " said

Sharon Ifft of the Allergy & Asthma Network Mothers of Asthmatics.

For one thing, there's still the pollution/asthma connection, which can't

be discarded, she said.

The tendency to have allergies and asthma is inherited, scientists

believe. But genes alone can't account for the huge increase in asthma

cases.

Smoking, even secondhand smoke, contributes to the problem. But

smoking rates in this country have dropped while asthma incidence

rises.

Whatever the cause ultimately turns out to be, there is no debating that

asthma is a growing problem.

The number of children younger than 5 who had the disease grew by

160 percent between 1980 and 1994, according to data from the

Centers for Disease Control and Prevention.

As of 1998, nearly 15 million Americans had asthma, and almost 5

million of them are children, according to the Asthma in America

nationwide study.

Asthma is blamed for more than 10 million missed school days each

year, according to the National Institutes of Health, and causes more

than 5,000 deaths in this country each year.