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Scientists Closer to Learning Why Good Hygiene May Foster Allergies

Scientists have wondered why people in Western countries get more asthma, allergies and autoimmune diseases than people from countries where hygiene is a problem. So William Parker, a researcher from Duke University in North Carolina, collected wild rats to compare their immune systems with those of animals raised in clean, laboratory conditions. He explains, "There's a really good chance that parasites and other infections change the immune system in a way that you don't have a propensity or a tendency to get allergies or autoimmune disease."

The wild rats - not surprisingly - were riddled with diseases and parasites. But Parker found -surprisingly - that they didn't react to common allergens the way the lab rats did. "So our wild rats' immune system is having a lot of things to worry about and it doesn't sweat the little things." He gives an example of a common allergen. "A little pollen grain that's coming by, it's going to just ignore that, whereas the person who's living in a very clean environment, or the lab rat, might be very concerned about a pollen grain and in fact might become allergic against it."

This finding is in line with a theory that says people from countries where there is widespread use of antiseptics end up developing more allergies than people from places with less sanitary living conditions. Parker says his findings also suggest people's immune systems need to be challenged more by dirt and disease during childhood. But he says that's difficult to test in humans. "You know a lot of people say if you let your kids get dirty they won't get allergies and autoimmune diseases. But doctors don't recommend that because we live in such crowded conditions that we get other diseases.

Parker is collecting more wild rats for further study.