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TUESDAY, March 6 (HealthDay News) -- Children growing up in the Amish culture in Switzerland have significantly less asthma and allergies than Swiss children who didn't grow up on a farm, according to new research.
The study could support the "hygiene hypothesis" that a too-clean world is causing today's urbanized kids to be more sensitive to allergens than their country cousins.
"In Europe, children living on traditional farms seem to have a very low prevalence of asthma and allergy," noted the study's lead author, Dr. Mark Holbreich, an allergist with Allergy and Asthma Consultants, in Indianapolis. In contrast, he said, "in the general population as many as 50 percent will have evidence of allergic sensitivity. They may not have all the symptoms of allergy, but they will test positive for sensitivity,"
But, "in Swiss children who live on farms, about 25 percent have allergic sensitivity," Holbreich said. "In Amish children, it was only 7 percent. There's something very protective in the Amish children."
He was scheduled to present the study's findings Sunday at the annual meeting of the American Academy of Allergy, Asthma and Immunology (AAAAI) in Orlando, Fla.
In the study, Holbreich and his colleagues in Switzerland sent out nearly 29,000 questionnaires to families of children between the ages of 6 and 12 years old. The Amish were given a modified version of the questionnaire.
A random sample of those who completed the questionnaires was selected to be given allergy testing.
"The Amish children (138) underwent skin tests," Holbreich explained, and "the Swiss farm children and non-farm children had blood tests for measurement of allergies. For the farm children 3,006 were tested by a blood test and 10,912 non-farm children were tested."
The study authors identified asthma cases by asking if a physician had ever diagnosed the child with asthma, Holbreich said.
Amish children had about half the prevalence of asthma compared to their non-farm-dwelling counterparts (about 5 percent vs. 11 percent). Swiss farm children had a rate of asthma of nearly 7 percent.
The rate of allergic sensitization followed similar patterns. Non-farm children had the highest rates, at about 44 percent, compared with 25 percent in the Swiss farm children and just above 7 percent among the Amish children.
So, what accounts for this striking difference? Holbreich said the researchers don't know for sure, but two factors appeared to be protective against allergy and asthma in the Amish children. One was that they drink raw [unpasteurized] milk directly from the cow, and the other was their exposure to large farm animals from a young age.
"When you have these exposures at a young age, that protection seems to be lifelong," said Holbreich.
He cautioned, however, that these finding in no way suggest that people should start giving their children raw milk, as it can harbor disease-causing germs.
But, the study's findings would seem to support the hygiene hypothesis, which is the idea that allergy and asthma are on the rise in today's world because the immune system isn't exposed to a variety of germs from a young age. This low level of exposure somehow creates dysfunction in the immune system, causing it to attack harmless substances, such as pet dander or peanut proteins.
Two other studies presented at the AAAAI meeting may also provide support for the hygiene hypothesis. One is a Korean study of about 1,800 children. It found that when antibiotics were given during infancy, children were more likely to develop allergies and allergic skin disease (eczema).
The other was a study from Johns Hopkins Hospital that looked at environmental exposures to chemicals. Researchers found that exposure to triclosan, a commonly used antibacterial agent found in hand sanitizers and mouthwashes, was significantly associated with allergies to food and airborne allergens, such as dust or pollen.
While the Swiss study found an association between Amish farm life and lower incidence of allergy and asthma, it could not prove a cause-and-effect relationship.
Dr. Jennifer Appleyard, chief of allergy and immunology at St. Hospital and Medical Center in Detroit, said one protective factor that the authors of the Amish study didn't mention is that the Amish live a fairly secluded existence and thus, have a fairly protected gene pool. Since genetics are one suspected aspect in the development of asthma and allergy, it may just be that the Amish aren't passing down the genes for those conditions, she reasoned.
"These are interesting things to think about, but there are so many confounding factors to look at. I don't think it's just Amish living or farm life. Genes play a role, access to care, environmental exposures. Maybe it's not that they're drinking raw milk, but that they're drinking milk without hormones. Or, they're not getting other environmental exposures that non-farm children are," she noted.
Because this research was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
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