By Michael Roizen, MD, and Mehmet Oz, MD

Iron Chef Masaharu Morimoto -- a superstar on Iron Chef America -- once said, “Japanese chefs believe our soul goes into our knives once we start using them. You wouldn't put your soul in a dishwasher!”

He’s right that modern utility isn’t very soulful -- but for a newly-discovered and surprising reason. A Swedish study found that kids who grow up in dishwasher-using households are more likely to develop allergies, eczema, and asthma than kids in households where dishes are hand-washed. (In the same vein, another study found that if parents clean off their kid’s pacifier by sucking on it, the children develop fewer allergies.)

The researchers followed over 1,000 seven and eight year olds. They found that 38% of kids whose parents had dishwashers reported eczema, while only 23% of hand-washers did. And in dishwasher families, 7.3% of the kids developed asthma, while only 1.7% of kids in hand- washing families did.

Why? Well, it could be another vote for the hygiene hypothesis. That theory says our lack of exposure to microbes makes us susceptible to autoimmune disease, allergies, etc. Perhaps, a dishwasher’s wash ‘n’ dry cycles don’t leave any immune-system-strengthening germs on dishes for us to ingest.

But we’re not saying give up your dishwasher (it may be soulless, but it sure is convenient), just don’t get over-sanitized. Lose the antibacterial soaps and household cleaners -- they trigger antibiotic resistance and their chemicals often include hormone disruptors! Trust your immune system. Soap, water and elbow grease to do a fine job.