You may think you're keeping your family healthy by sanitizing every dishload in a leave-no-bacteria-behind dishwasher, but a new study suggests good old-fashioned hand-washing may lessen kids' chances of developing allergies, the New York Times reports. As per a study published in Pediatrics, scientists studied more than 1,000 7- and 8-year-olds living in two areas of Sweden and found that children in households where dishes were hand-washed had a 40% lower risk of developing allergies such as eczema or asthma, compared to those with dishwashers, LiveScience reports. The results appear to be another notch for the "hygiene hypothesis," which contends kids in developed countries often live in excessive cleanliness, which shelters them from low bacteria levels that could naturally build immunity, NPR notes.
The scientists also looked at other behaviors, such as whether kids consumed fermented foods or fare from local farms (both of which are said to have higher bacteria count than other types of food); the allergy risks of kids eating off hand-washed dishes seemed to dip even lower with those factors included, LiveScience notes. Researchers point out, however, that disparate other factors—such as lower income levels, having older siblings, and living on a farm as children—have also been linked to lower allergy levels, per LiveScience. "It's very intriguing and lends one more 'X' on the column for the hygiene hypothesis," an allergist and American Academy of Pediatrics member tells NPR, though he acknowledges more study is needed and that people shouldn't necessarily stop buying dishwashers. (Scientists recently made what they hope will be a giant step toward curing peanut allergies.)