STEVE INSKEEP, HOST:
Now let's report on kids who are safely at home, but maybe not quite as safely as their parents think. Research suggests a link between using a dishwasher and kids developing allergies. NPR's Rob Stein reports.
ROB STEIN, BYLINE: There's a scientific theory called the hygiene hypothesis, and it basically says this - people in developed countries are growing up way too clean. We use too much hand gel, too many detergents, go way too crazy trying to sterilize our lives. Bill Hesselmar studies the hygiene hypothesis at Gothenburg University in Sweden.
BILL HESSELMAR: We think it's good to be exposed to bacteria, especially early in life, and that's the hygiene hypothesis.
STEIN: Because being exposed to bacteria early in life trains babies' immune systems how to work. And if they don't get this training, their immune systems are more likely to misfire and overreact causing lots of diseases like allergies, eczema, asthma. So Hesselmar and his colleagues have been trying to figure out some of the simple day-to-day ways we're being too clean. In their latest research, they took a look at how people wash their dishes, whether they use a dishwashing machine or just wash their dishes by hand.
HESSELMAR: The hypothesis was that these different dishwashing methods, they are not equally good in reducing bacteria from eating utensils and so on. So we thought that perhaps hand dishwashing was less effective so that you are exposed to more bacteria.
STEIN: Which would be good, according to the hygiene hypothesis, assuming they're not the kinds of bacteria that make people sick. And in this week's issue of the journal Pediatrics, the researchers report what they found by studying 7- and 8-year-old kids living in more than a thousand families in Sweden.
HESSELMAR: In families who used the hand dishwashing, the children had less allergy. It was reduced by about 50 percent.
STEIN: They were about half as likely to develop asthma, eczema or hay fever.
HESSELMAR: It is very interesting, I think, that very common lifestyle factor like dishwashing that we could see effects on allergy development.
STEIN: Other researchers say the new study may be onto something. Todd Mahr is an allergy expert at the American Academy of Pediatrics.
TODD MAHR: I think it's very intriguing and lends one more, you know, X on the column for the hygiene hypothesis, that maybe how we live does influence whether we develop allergies.
STEIN: But both Hesselmar and Mahr caution that much more research is needed to prove that the increasing use of dishwashing machines may be one reason why allergies in kids are skyrocketing. So they're not ready to recommend parents stop using dishwashers to protect their kids.
MAHR: If you're looking at, we have only a certain amount of money and we're looking at buying a dishwasher or we're looking at spending it on something else, well, this might give you an argument to say, well, maybe spend it on something else if that fits into your lifestyle choice, OK? Some people may say, I really don't like doing dishes (laughter). I want a dishwasher. And it's like, well, you know, I'm not convinced that that's going to make that big a difference.
STEIN: But for people who like doing dishes, Hesselmar says it probably wouldn't hurt and just might reduce the chances their kids will get allergies, asthma and other problems caused by living in a world that's too clean. Rob Stein, NPR News.
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