A simple experiment involving hand dryers has gone viral over the last few days, with many people now committed to doing a Taylor Swift and shaking it off from now on.
The video from TikTok user @phonesoap shows the experimenter collecting bacteria samples by first waving a petri dish through the air to simulate drying your hands by shaking them, and then collecting samples from various different types of hand dryer.
The samples are then left to incubate for three days, to see what grows on there.
The dish simulating merely shaking your hands dry fared the best, with no visible growth – while hand dryers at a gas station produced the most bacterial growth. While not exactly a large-scale study, it was enough to swear people off hand dryers for good, with one user on TikTok describing them as "the wind of a thousand farts".
So, is there anything to this? Well, sorry but yes. Several studies from the University of Leeds School of Medicine have shown that hand dryers promote the spread of bacteria.
In one experiment, to simulate badly-washed hands, researchers contaminated people's hands with a harmless bacteria called Lactobacillus that's not normally found in bathrooms. They then dried their hands using jet hand dryers, warm air hand dryers, and paper towels. Samples were then taken from around the hand dryers and a short distance away. Levels of Lactobacillus in the air around jet air dryers were found to be 4.5 times higher than around warm air dryers, and a whole 27 times higher than around paper towel
“Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it," Professor Mark Wilcox, who led the experiment, said in a statement. "You may also be splattered with bugs from other people’s hands."
In a follow-up study in hospitals in the UK, France, and Italy, the team placed jet hand dryers, hot air hand dryers, and paper towel dispensers in hospital bathrooms, at separate times over a 12-week period. They then measured bacteria levels while each of these hand-drying methods was in use.
“We found multiple examples of greater bacterial contamination on surfaces, including by faecal and antibiotic-resistant bacteria, when jet-air dryers rather than paper towels were in use," Wilcox said in a press release. "Choice of hand drying method affects how likely microbes can spread, and so possibly the risk of infection.”
Wilcox adds that the problem is that people do not wash their hands properly – though hopefully, this has changed since the stress placed on good hygiene at the beginning of the COVID-19 pandemic.
“When people use a jet-air dryer, the microbes get blown off and spread around the toilet room," he added.
“In effect, the dryer creates an aerosol that contaminates the toilet room, including the dryer itself and potentially the sinks, floor and other surfaces, depending on the dryer design and where it is sited. If people touch those surfaces, they risk becoming contaminated by bacteria or viruses."
Following the experiment, they recommended hospitals no longer use jet air dryers.