You might want to think twice before reaching your hands under a hot-air dryer after using a public restroom. Because you could be covering your freshly cleaned hands — with more bacteria.
A 2018 study conducted a test to determine if hand dryers in public bathrooms could be dispensing bacteria onto people's hands. To investigate this, researchers exposed petri dishes to the air in bathrooms in various conditions, and brought the dishes back to their lab to see if bacteria was growing on them.
What they found was that "petri dishes exposed to bathroom air for two minutes with the hand dryers off only grew one colony of bacteria, or none at all," according to a Harvard Health article written about the study.
But, "petri dishes exposed to hot air from a bathroom hand dryer for 30 seconds grew up to 254 colonies of bacteria (though most had from 18 to 60 colonies of bacteria)."
Despite that slightly alarming discovery, you can still wash and dry safely. Here's how.
Here's how to safely dry your hands
Health experts say you should still dry your hands after washing them, but consider these options when you do:
- Use paper towels to dry your hands instead
- Refrain from using jet air dryers because they're most associated with spreading germs in bathrooms from hand dryers
Also, keep in mind that the highest risk for most of the bacteria detected in the hand dryers are for people in hospitals or those with weakened immune systems.
"And remember that your chances of picking up a serious pathogen in a restroom are small. Direct contact with other people is much more likely as a means of acquiring infection," Dr. John Ross, an assistant professor of medicine at Harvard Medical School, wrote in the university's article.
Here's what else was discovered about the bacteria in hot-air dryers.
The source of the bacteria? Toilets
To the researchers behind the study, it was unclear at first whether the bacteria were increasing within the hand dryers, or if they were being sucked into the dryers from the bathroom air.
So, scientists attached high-efficiency particulate air (HEPA) filters to the hot-air dryers to decrease as much of the bacteria from the bathroom air as they could, before it was able to enter the dryers.
Doing so decreased the bacteria in the petri dishes by 75%, thus proving that most of the bacteria was coming from the bathroom air.
It turns out that, "every time a lidless toilet is flushed, it aerosolizes a fine mist of microbes," Ross wrote.
These small particles which Ross calls a "fecal cloud," can spread out as far as six square meters which is equivalent to 65 square feet, he added.
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