Study explores link between dishwashers and kids' allergy risk

The dishwasher is a modern miracle, saving us precious time during our post-meal cleanups. But could this modern convenience also be at fault for the rise in kids' allergies and eczema?

"Allergy in Children in Hand Versus Machine Dishwashing," published in this month’s Pediatrics, found a lower rate of allergic disease development in kids from families who hand-wash their dishes compared to those who use a dishwasher. The study builds on existing research that suggests kids should have a little dirt around them to keep healthy.

The “hygiene hypothesis” is based on the idea that allergies are on the rise because we keep our houses—and our kids—too clean. Children need exposure to bacteria early in life strengthen and boost their immune systems. Other recent studies have found that using antibacterial soap can increase the chance of developing allergies, while having pets, living on a farm and even spit-washing your baby’s pacifier can decrease the risk.

The lead author of the dishwasher study, Dr. Bill Hesselmar—who also authored of the spit-washing study—of Queen Silvia Children’s Hospital in Gothenburg, Sweden, explained the theory to Time: “If you are exposed to microbes, especially early in life, you stimulate the immune system in various ways and it becomes tolerant,” he said.

For this study, Dr. Hesselmar's team surveyed more than 1,000 parents of seven- and eight-year-olds in two areas of Sweden. Parents answered a series of questions, including how they wash their dishes and if any family members had allergies. He found that 23 percent of kids whose families hand-washed their dishes had eczema, compared to 38 percent of kids whose families used a dishwasher.

It's important to note that the study shows an observational link that may or may not be causal (in other words, it may very well be that higher allergy rates and dishwasher use are not related). Dr. Hessellmar says it's too early to recommend parents hand-wash the dishes to reduce allergy risk—further study is needed before we start throwing out dishwashers.

Researchers are now exploring whether it's the act of dish-washing (unlikely as many kids are too young to do it consistently), the long-term use of hand-washed dishes (because more bacteria would be left behind on them compared to dishes run through the dishwasher), or some other factor that's responsible for the reduced risk of eczema. Another drawback to the study is that exposure to germs and bacteria help the immune system before approximately six months of age, and few kids would be feeding from hand-washed bottles that weren't also sanitized in boiling water.

For me, the dishwasher is a sanity-saver and I would want to see a mountain of causal evidence before I started hand-washing all the dishes in my house.

Emma Waverman is a writer, blogger and mom to three kids. She has many opinions, some of them are fit to print. Read more of her articles here and follow her on Twitter @emmawaverman.