Is This Common Household Appliance Threatening Your Kids’ Health?

You may believe you’re doing your family a service by investing in a dishwasher—not only are they a time saver, they're scientifically shown to be more effective than hand washing when it comes to removing bacteria from tableware, glassware, pots, and pans.

But a new study has raised an interesting question about how clean is too clean when it comes to children who suffer from allergies and eczema. (Eczema is an inflammatory skin condition that causes intense itching and redness; it’s not necessarily an allergic condition, but research has shown an association between various environmental and food allergies and the development of eczema.)

The Hygiene Hypothesis

According to the so-called "hygiene hypothesis," people in the U.S. and other developed countries are so devoted to cleanliness and the eradication of germs that we have ended up creating generations of children whose immune systems never get exposed to many common pathogens—and who then develop allergies. (A pathogen is any microorganism that causes disease by infecting body tissues and reproducing.)

The thinking is as follows: Because our environment is so sterile, when children do encounter natural proteins like animal dander, pollen, or food particles, instead of developing a tolerance, their immune systems mount an exaggerated response, possibly as a direct result of this previous lack of exposure.

"It’s a fascinating concept that many of us believe is probably the most logical explanation [for the rise in allergies and eczema]," says Devang Doshi, MD, director of the division of pediatric allergy and immunology at Royal Oak Beaumont Hospital in Royal Oak, Michigan. In effect, are our surroundings too healthy? Are children not being exposed to natural infections early enough to remain tolerant (i.e., symptom-free) when exposed to environmental and food proteins?

What the Latest Research Shows

Preliminary results of a recent study appear to bear out this theory. Researchers at Sweden’s University of Gothenburg queried the parents of more than 1,000 schoolchildren to find out if the children had allergies or eczema. They also asked parents about diet and lifestyle: did the children eat foods that were fermented or that came directly from farms? And were dishes washed by hand or machine?

The results showed that children whose families washed dishes by hand had lower rates of eczema (23%) than those from families that used a dishwasher (38%), as well as lower rates of asthma (1.7% compared to 7.3%). Eating fermented or farm-grown foods also contributed to markedly lower rates of allergies and eczema.

Say Goodbye to Dishwashers?

So should we all ditch our dishwashers and revert back to washing everything by hand in order to expose our families to the widest possible array of immunity-building bacteria? Not necessarily. For one thing, such measures would need to be taken very early in a child’s life; once an allergy has developed, switching to hand washing won’t have any effect. And experts note that it’s too early to make broad recommendations based on a single study in a single country. As Joyce Rabbat, MD, points out, "This study showed an inverse association with hand washing and allergic disease [that is, a lower incidence of allergies among families that hand washed dishes]—but it is not necessarily causal," meaning the use of dishwashers isn’t necessarily causing the allergies. The director of the division of pediatric allergy and immunology at Loyola University Medical Center in Maywood, Illinois, continues, "The other limitation is that hand washing dishes may be one of many lifestyle factors that resulted in the reduced risk of allergic disease in those families."

Tips for Parents of Allergic and Asthmatic Kids

What can you do if your children already have allergic disease? "Parents of children who suffer from seasonal allergies and/or asthma can minimize their symptoms by closely following their doctor’s recommendations for both prescribed and over-the-counter medications," says Doshi. In addition, "Well-controlled maintenance medications for asthma should enable the children who use them to function normally both at rest and during exercise."

Other Tips:

  1. When pollen counts are high, avoid prolonged outdoor exposure. (For more info on the pollen count in your area, visit the American Academy of Allergy Asthma & Immunology’s National Allergy Bureau.)
  2. Keep doors and windows closed. For fresher air, use a central fan or air-conditioning unit that uses a HEPA (High-Efficiency Particulate Air) filter.
  3. Change clothing and/or shower after extended outdoor activities.

Devang Doshi, MD, reviewed this article.


Doshi, Devang, MD. Phone conversation with source. May 7, 2015.

Rabbat, Joyce, MD. Email exchange with source. May 13, 2015.

Hesselmar B., A. Hicke-Roberts, G. Wennergren. "Allergy in Children in Hand Versus Machine Dishwashing." Pediatrics 135, 3 (2015): e590-e597. doi: 10.1542/peds.2014-2968.

"Infectious Diseases: Pathogens." The Association of the British Pharmaceutical Industry. Accessed May 22, 2015.

"National Allergy Bureau." Academy of Allergy Asthma & Immunology. Page accessed June 2, 2015.