As cold and flu season approaches, new research sheds light on a little-studied aspect of hand-washing: how to dry your hands. Paper towels are the best option for keeping germ counts low, the study reports, while rubbing hands under a warm-air dryer may potentially do more harm than good.
What do we know already
The simple act of regularly washing your hands can reduce your chances of catching the flu and other illnesses. Good hand washing is also important after handling raw meat and doing other tasks that might expose you to Salmonella and other harmful bacteria. Most hand-washing guidelines recommend washing with soap and warm water for at least 60 seconds.
However, these guidelines provide little insight about how best to dry your hands. This is somewhat surprising, given research showing that damp hands are more likely to transfer lingering germs onto other surfaces, and that thoroughly drying your hands can reduce the risk of such transfer by up to 99 percent.
The usual drying options in public facilities are paper towels and warm-air hand dryers. A newer type of hand dryer is also becoming more widely available. Rather than heat, it uses high-speed air jets to remove water from the hands.
But which of these methods works best? To find out, researchers enlisted 14 volunteers for a two-part study on drying techniques.
What does the new study say?
The first part of the study focused on the different types of dryers. After handling raw chicken, the participants washed with soap and water, and then dried their hands with an air-jet dryer or a warm-air dryer. They next pressed their hands on aluminium foil and the researchers checked how much bacteria they left behind.
When the dryers were used for 10 seconds, the air-jet dryer worked best at drying the hands and reducing the transfer of bacteria. However, the two types of dryers had similar results when the warm-air dryer was used for 30 seconds.
In the second part of the study, the researchers checked for bacteria in the participants' palms, fingertips, and fingers right after they'd rinsed their hands and again after they'd dried them with a paper towel, an air-jet dryer, or a warm-air dryer. When using the warm-air dryer, people were instructed either to rub their hands or to hold them still. (The air-jet dryer doesn't allow for hand-rubbing, as the hands are placed side-by-side within the dryer.)
The researchers found that bacteria levels were reduced by about the same amount with either type of dryer if people didn't rub their hands. However, if they rubbed their hands while using the warm-air dryer, their bacteria levels weren't reduced by nearly as much and even increased in some parts of their hands, such as in the middle of their fingers. This may be because rubbing the hands can release resident bacteria living in the pores of the skin. Although these bacteria aren't likely to be harmful to the person washing their hands, they could cause health problems if transferred to people with weakened immune systems or open wounds, say the researchers.
The study found that paper towels worked better than either type of dryer for reducing bacteria.
How reliable are the findings?
This was a well-conducted study and its results should be fairly reliable. However, it included only 14 people, and each participant was tested using the various drying methods over several days. These findings would be stronger if a larger group of people had been tested.
Where does the study come from?
The study was conducted by researchers at the University of Bradford and a company called Dyson Limited, which funded the study and makes the air-jet dryer. It's not unusual for manufacturers to do studies that test their own products. But it's important to keep this in mind when reviewing the study's results.
The study was published in the Journal of Applied Microbiology, which is owned by the Society for Applied Microbiology.
What does this mean for me?
This research suggests that paper towels are the best hand-drying tool for ridding your hands of bacteria. Air-dryers can also work reasonably well, with air-jet dryers doing the job more quickly than warm-air dryers. But if you use a warm-air dryer, you may get similar results by holding your hands under the dryer for the full drying cycle (around 30 seconds) and not rubbing your hands together.
And regardless of the drying method you use, keep this in mind: to best prevent the spread of bacteria and other germs, make sure your hands are thoroughly dried as well as thoroughly washed.
What should I do now?
From:
Snelling AM, Saville T, Stevens D, et al. Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers. Journal of Applied Microbiology. Published online 7 September 2010.
To read more, see our information on flu and swine flu.
