Drying your hands by shaking them may actually be the best way to keep them clean, a citizen scientist investigation suggests.
To study whether hand dryers put bacteria back on your hands, Dallin Lewis, 33, held petri dishes under the machines at a public restroom, gas station, movie theater and convenience store in Provo, Utah, for a few seconds.
After incubating them for three days, the vessels were found to be full of bacteria and fungi – which appeared in white, yellow and black spots. The dryer in the public bathroom turned out to be the dirtiest.
But a separate petri dish that was waved in the air in the bathroom before being incubated to mimic “air-drying” of the hands remained completely clean.
Lewis, who conducted the tests near his home in Provo, Utah, for his TikTok channel, said the results were “much worse” than he expected. “I’ve done a lot of similar tests for bacterial growth on different surfaces – phones and petrol pumps are probably some of the worst – but the hand dryer was so bad!” he said.
It comes after a British expert warned yesterday that not drying your hands after going to the toilet could be even worse than not washing them at all. Dr. David Weber, a microbiologist with 50 years of experience, even said that people who do not wash their hands properly can be described as a social menace.
PUBLIC BATHROOM: For the experiment, Dallin Lewis, 33, began by examining a hand dryer in a public bathroom in Provo, Utah. Three days after holding the petri dish under it, he found several colonies of bacteria
GAS STATION: A petri dish was also held under a dryer at a gas station for a few seconds. It was then incubated and – like the one in the public bathroom – quickly exploded with bacteria
CINEMA: The petri dish was also stuck in a hand dryer in a movie theater. After being incubated, it also showed the appearance of a collection of white spots – indicating small bacterial colonies
SHOP DRYER: A petri dish was also placed under a shop dryer for a few seconds. After it was incubated for three days, several white spots also appeared – indicating the presence of bacteria
AIR DRYING: During the experiment, the petri dish was also shaken in air to mimic “air drying” of the hands. It produced virtually no bacteria after being incubated for three days
Lewis decided to investigate how much bacteria was being killed by hand dryers after realizing that one based near his home was full of microorganisms.
A visual assessment revealed that the hand dryer in the public bathroom shot up the most bacteria – and was the only one that even had black colonies – along with the one in the gas station.
Petri kept under the dryers in a movie theater and a store produced only a few white spots a few days later, much less than the others. But the one that was “air dried” was almost clear—the best result.
Speaking to SWNS, Lewis, who works for personal item sanitizing company PhoneSoap, said he was “incredibly surprised” by the test results. “I knew they were going to be bad, but by no means did I expect the level I saw,” he said.
No tests were conducted to determine what bacteria and fungi might be lurking in the dryers, and the researchers did not examine the effects of drying hands with a paper towel.
But previous research has shown that hand dryers can shoot bacteria onto people’s hands as they suck up the air around them – where microorganisms can take hold.
The tests also revealed hidden bacterial colonies on the nozzles of the hand dryers.
Experts say it’s extremely important to dry your hands after washing because many types of bacteria like to thrive in warm, moist places.
E.coli – a bacteria that can cause food poisoning – thrives on moist surfaces, including hands. Previous research has shown that 85 percent of germs spread by people contaminating surfaces occur when hands are still damp.
But there are a number of different ways to dry them – including using a paper towel, a hand dryer or shaking them in the air.
To help iron out the differences, Weber, microbiologist with 50 years of experience, including at the University College of Swansea in Wales, ranked eight of the most popular hand drying methods in the world.
At the top comes the “surgeon” — running fingers through every nook and cranny under a hand dryer. This will help ensure that your hands are completely moisture-free and bacteria-free.
Perhaps obviously, the so-called “drying drip slop” – who doesn’t bother to dry their hands at all – ranks at the opposite end of the scale.
Dr Weber, who works alongside Airdri, a company that makes hand dryers, said: “Bacteria thrive on moist surfaces, including hands.
“The pandemic has focused attention on the correct way to wash our hands with published guidelines from the WHO, CDC and NHS.
Experts say not drying your hands can be just as bad as not washing them at all. The researchers said public guidelines on hand drying are needed to stop the spread of bacteria and viruses. Graphic: List of eight hand drying methods, ranked from best (top left) to worst (bottom right)
“However, there is no such guidance on proper hand drying procedures, which are equally important.”
He added: “Drying hands incorrectly can be less hygienic than not washing them at all.
“Research has shown that bacterial transfer is directly related to the time and effectiveness of hand drying, bacterial transfer progressively decreases as water is removed.”
Dr Weber, who works alongside Airdri, a company that makes hand dryers, said: “Bacteria thrive on moist surfaces, including hands.
“The pandemic has focused attention on the correct way to wash our hands with published guidelines from the WHO, CDC and NHS.
“However, there is no such guidance on proper hand drying procedures, which are equally important.”
He added: “Drying hands incorrectly can be less hygienic than not washing them at all.
“Research has shown that bacterial transfer is directly related to the time and effectiveness of hand drying, bacterial transfer progressively decreases as water is removed.”
Likewise, wiping off any remaining moisture on your pants or skirt after drying can pick up any bacteria on your clothes, defeating the purpose of hand washing.