European researchers think dishwashers could be making children more susceptible to allergies. A recent study out of Sweden's University of Gothenburg found kids living in families that washed their dishes by hand were roughly 40 percent less likely to develop allergies like eczema, asthma and hay fever. The theory behind it -- called the hygiene hypothesis -- is based on the idea that children have weaker immune systems when they grow up in ultrasanitized homes.

"I think it is very interesting that with a very common lifestyle factor like dishwashing, we could see effects on allergy development," pediatric researcher Bill Hesselmar told NPR. The study was due to be published online Monday in the journal Pediatrics.

Parents who hand wash dishes may not be as thorough as a machine, Hesselmar told the New York Times. They may inadvertently fail to remove some bacteria, in turn exposing kids to more germs and strengthening their immune systems. Children who regularly eat fermented foods and direct-from-farm foods like unpasteurized milk could see similar benefits.

But LiveScience reported the study's findings don't necessarily mean everyone should change their dishwashing practices at once. It's too soon for scientists to draw concrete conclusions on the subject, especially because other lifestyle factors -- like how many people kids live with, what their immigration status is and whether they wash their hands -- could also influence immunity.

Still, Wisconsin allergist Todd Mahr told NPR the information could be helpful for some. "If you're looking at, 'We have only a certain amount of money, and we're looking at buying a dishwasher or spending it on something else?' This might give you an argument to say, 'Well, maybe spend it on something else,'" Mahr said.

The study examined 1,029 Swedish children between the ages of 7 and 8.