Mind & Body

Hand Dryers Are Blowing Bacteria All Over Your Hands

Using a public restroom always makes us slightly ... queasy. They're just full of things other people have touched, from doorknobs to toilet flushers to the bathroom sink. And you know that not all of those people washed their hands. Good thing you always wash your hands — but nine times out of 10, you then stick them in a bacteria-spreading factory.

Related Video: Are You Washing Your Hands Incorrectly?

Dry, Dry Again

Yes, it's true. If it's bacteria you're worried about, hot-air hand dryers are basically the last place you're going to want to put your hands. According to a new study led by Luz del Carmen Huesca-Espitia from UConn Health, those jets are pulling in bacteria from the bathroom air and blowing it out again all over your hands. The evidence is pretty undeniable. Huesca-Espitia exposed petri dishes to hot air dryers (with no hands involved) in different conditions — some sat undisturbed for two minutes beneath an inactive one, and others were directly exposed to 30 seconds of the hot air. All of the dishes that had sat in peace grew a maximum of one colony of bacteria. But those exposed to a blast from the hand dryer? Most grew about 18 to 60 colonies, and some had as many as 254.

When the researchers installed high-efficiency particulate air (HEPA) filters on the dryers to cut down on the bacteria the devices took in, they produced about 75 percent fewer colonies. It's kind of obvious when you think about it. That air in the dryer has to come from somewhere, and bathroom air isn't pristine — lidless toilets have been known to spread bacteria over a 65-square-foot (six-square-meter) area, after all. But at least the experiment with the filters showed that the bacterial colonies aren't spreading inside the dryers themselves.

Blown Out of Proportion

Let's be clear: Huesca-Espitia and her team aren't saying that you're better off not drying than using a hot-air hand dryer. It's a lot easier for bacteria to survive on wet hands, and you're more likely to spread them around that way. Also, most of the bacteria that the team discovered on the dryer-blown dishes were harmless, and those that weren't were at least benign for healthy people. Finally — and this cannot be understated — their experiment was carried out in a scientific research facility where many other people were working with bacteria on a daily basis. Undoubtedly many of the bacteria tracked in this study originated not in the bathroom but in another scientist's lab.

Still, if you've got hand-drying options, you might want to opt for the less-infectious choice. Paper towels are still on top as far as that goes, ranking the best for both maximum dryness and maximum bacteria reduction (and as far as eco-friendliness goes, they're about even with traditional hand dryers). Dispenser options matter too — the automatic paper towel machines that minimize contact with previous users the most will keep your hands the cleanest, while those rolling cloth dispensers where everyone shares the same long towel get you uncomfortably close to the last person's wet spots.

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Want to learn even more about how to protect yourself from germs? Check out "Wash Your Hands: Dirty Truth About Germs, Viruses and Epidemics...and the Simple Ways to Protect Yourself in a Dangerous World" by Dr. Frédéric Saldmann. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Reuben Westmaas May 25, 2018

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