For millions of people, allergies are at best a nuisance and at worst a serious health concern. Their cause (or at least their increased prevalence) is something of a mystery, but a new Swedish study has found yet another factor that may hinder their development in children: Washing dishes with good, old-fashioned elbow grease.
“If you are exposed to microbes, especially early in life, you stimulate the immune system in various ways and it becomes tolerant,” says study author Dr. Bill Hesselmar of Queen Silvia Children’s Hospital in Gothenburg, Sweden. “We thought [hand washing dishes] might be important, but we didn’t know, so we asked that question.”
The idea is that microbial exposure acts somewhat like a vaccine when permitted in the right amounts at the right age. Similar studies found that other factors like having pets, eating fish and living on a farm also have a mitigating effect. For children without the convenience of a family-owned farm, even ample time playing outside in the dirt is associated with a decreased risk of allergies.
The study was a survey of 1,029 Swedish parents and guardians of children ages seven to eight. They found that in homes where dishes were hand-washed, only 23% of children had a history of eczema, versus 38% in homes with dishwashers. Overall, the average risk of eczema in hand-washing homes was 57% of those that used machines, with a 95% confidence interval ranging from 37% to 85%.
The study is not meant to suggest that use of a dishwasher promotes allergies; rather, the mitigation effects of hand-washing is a result of inefficiencies: Because hand-washing leaves behind more bacteria, the diluted exposure over time is thought to have similar preventative benefits as other exposure strategies. The benefits did not rely on the children to wash the dishes themselves.
The researchers also found that when the children ate fermented and farm-fresh foods off of those same hand-washed dishes, their chances for developing allergies fell even lower.
The study does not explain why this works despite hand-washing often calling for anti-microbial soaps, nor does it address other allergy-related illnesses. The researchers have the same questions, and intend to study it further.