Moms and dads -- grab a sponge and step away from the dishwasher.
A new study suggests that hand-washing dishes (and leaving some microbes on a fork, bowl, or plate in the process) may help reduce the risk of allergy development in young children.
In a paper published Monday in the journal Pediatrics, Swedish researchers report that kids who grew up in households where dishes are hand-washed as opposed to sterilized in a dishwasher were less likely to report suffering from eczema, asthma, or hay fever.
They also found that eating fermented foods (such as sauerkraut or pickles) and eating eggs and milk purchased directly from a farm lowered a child's risk of developing allergies.
The findings are in line with what is called the hygiene hypothesis, which suggests that excessive cleanliness is responsible for a growing allergy epidemic. The idea is that exposure to germs in early childhood is necessary to stimulate the immune system and reduce the risk of allergy development.
The theory has been borne out in several different studies. For example, research shows that kids are less likely to become allergic if their parents suck a pacifier to clean it, if they grow up on farms, and if they have pets early in life.
The study is based on a questionnaire filled out by the parents of 1,029 Swedish children aged 7 to 8.
A history of eczema was reported in 23% of children whose parents washed dishes by hand and in 38% of those who used a machine dishwasher.
Asthma was reported in 1.7% of kids whose parents hand-wash dishes compared to 7.3% for those who use a dishwasher. For hay fever it was 10.3% and 12.9%, but the researchers say this difference was not statistically different.
The authors also created an umbrella term, "traditional cooking," which includes washing dishes by hand, eating fermented food, and buying food directly from farms.
After controlling for several factors including day care attendance, parental history of allergy and whether or not the family had a pet, they found that 19% of kids from "traditional cooking" families reported suffering from allergies, compared to 46% of kids who came from families where the dishes went in the dishwasher, the food was not fermented, and nothing came straight from the farm.
The research team, lead by Bill Hesselmar of Queen Silvia Children's Hospital in Gothenberg, Sweden, say the goal of their study was to uncover practical habits that might protect against allergies.
The researchers note that several studies have shown that living on a farm is associated with lower rates of allergies in children, but that might be a hard prescription for most families to follow.
On the other hand, increasing a child's exposure to microbes through washing dishes by hand and other elements of "traditional cooking" might be doable.
"Even though we do not currently have strong support for recommending any of these lifestyle factors in allergy prevention, they are already commonly used and most often regarded as harmless," the authors write.