Thursday June 6 2013
The study found that most people prefer using paper towels
The Mail Online has encouraged readers to "ditch the hand dryers", as "paper towels are more hygienic". The debate on the relative merits of paper towels versus hot air dryers may appear trivial, but the issue can be a matter of life and death.
Hand drying is an essential part of the hand washing process, as wet skin helps spread bacteria. In environments where people are vulnerable to the effects of infection, such as hospitals, thorough hand washing and drying could save lives.
The Mail reports on a review of 12 studies looking at how hygienic different hand drying techniques are. To borrow a pun from the Mail, it looks like paper towels win "hands down".
The review found the advantages of paper towels include that they dry the hands more quickly, remove more bacteria and are less likely to lead to cross-contamination. However, the review's authors did not include details of the methods used in the studies involved, so it is difficult to assess how valid their results are.
Unfortunately, we usually don't have much choice about the type of drying method we use in public or workplace bathrooms. The most important thing to remember is that whatever drying facilities are provided, it is just as important to dry your hands thoroughly as it is to wash them thoroughly with soap.
Where did the story come from?
The study was carried out by researchers from Queensland University of Technology and other organisations in Australia and China. No funding source was reported.
It was published in the peer-reviewed medical journal, Mayo Clinic Proceedings.
Mail Online covered this review reasonably well, although the limitations of the review were not mentioned.
As an aside, the study is actually from 2012, so it is a little puzzling why it is hitting the headlines now.
What kind of research was this?
This was a narrative review of the evidence on the effectiveness of hand drying techniques to prevent the spread of bacteria. The review included studies published since the 1970s.
Bacteria is more likely to be passed from wet skin than dry skin, making proper hand drying an essential component of the hand washing process in order to prevent the spread of infections.
This prevention of the spread of infection is especially important in settings such as hospitals and clinics. The authors sought to identify the most effective drying technique and make recommendations on its use for healthcare professionals.
What did the research involve?
The study authors searched several databases for studies that compared at least two hand drying methods and reported results on different aspects of hand drying effectiveness. The various factors considered were:
- amount of water removed
- effectiveness of removal of bacteria
- prevention of cross-contamination
The authors compared several techniques, including paper towels, cloth towels, electric hot air dryers, jet air dryers and evaporation (air drying).
This was a narrative review, so the authors didn't statistically pool the study results as would be the case with a meta-analysis. Based on the analyses presented in each identified study, the researchers are able to suggest how the various techniques compare. However, they did not provide a pooled statistical estimate of effectiveness for each technique.
What were the basic results?
The researchers identified 12 articles that were included in the review.
Two studies assessed how efficiently different methods removed water from the hands. The authors report that:
- one study compared cloth towels with hot air dryers and found that 10 seconds of drying with a cloth towel was approximately equivalent to 45 seconds of using a hot air dryer
- the other study found that 10 seconds of drying with either paper towels or jet air dryers was equally efficient at removing water, while hot air dryers took about 40 seconds to achieve the same level of dryness
Bacteria removal and drying method
Seven studies assessed the effectiveness of different techniques of removing bacteria from the hands and reported inconsistent results.
One study found that paper towels reduced the number of all types of bacteria, air dryers increased their number, while jet air dryers increased the number of some, but not all bacteria. The increases seen from jet air dryers were less than those seen with hot air dryers.
Another study found that hot air dryers were the least effective method of removing bacteria.
Two studies that looked at various drying methods reported no difference in the amount of bacteria left on the hands.
Another study reported that using a hot air dryer with ultraviolet light for 30 seconds was more effective than paper towels, but that rubbing the hands together under a hot air dryer was less effective.
However, a final study reported that 10 seconds of holding the hands still under a hot air dryer was better at removing rotaviruses and E. coli than 10 seconds using either paper or cloth towels.
Bacteria removal and drying technique
One study found that 10 seconds of using a hot air dryer was associated with more bacteria on the hands than not using a dryer at all. It found that rubbing the hands together under a hot air dryer prevented bacteria removal. Using a jet air dryer for 10 seconds was found to be more effective at removing bacteria than using a hot air dryer for 30-35 seconds. This study also reported that using a paper towel was the best method of removing bacteria, especially from the fingertips.
One of the studies found that rubbing the hands together under a hot air dryer for 15 seconds significantly increased the amount of bacteria on the hands, while holding the hands still under the dryer for the same amount of time decreased the amount of bacteria, although it's not clear whether this was significant. This study also found that paper towels were more effective at removing bacteria from the fingertips than from the palm of the hand and fingers.
When examining the effect of the methods on bacterial transmission or cross-contamination, the researchers found one study that investigated the risk of cross-contamination in a hospital setting. It compared the spread of bacteria using a hot air dryer versus using paper towels and found that the electric dryers spread the bacteria up to three feet (about a metre) from the unit, while no dispersal was found when using paper towels.
A second study reported that hot air dyers led to a large number of airborne bacteria near the dryer, but no such spread was seen with either paper or cloth towels.
A third study found that jet air dryers in a washroom were found to spread bacteria up to two metres (around six feet), while paper towels and hand dryers were better at not contaminating the washroom.
How did the researchers interpret the results?
The authors concluded that, "From a hygiene viewpoint, paper towels are superior to electric air dryers" and that, "drying hands thoroughly with a single-use, disposable paper towels is the preferred method of hand drying in healthcare".
This review suggests that using paper towels to dry the hands is more effective than other methods at actually getting the hands dry, reducing the amount of bacteria on them, and preventing contamination of the washroom environment.
There are, however, limitations to this review that should be considered before concluding that hot air dryers or jet dryers are ineffective:
- The review did not report the quality of the various studies included. When determining whether the results of a study are valid, it is important to establish whether the research methods were sufficient to minimise bias and confounding. As the review did not report this, it is unclear how valid the studies' results are.
- The studies' methods varied and this could influence the consistency of results across the experiments. The amount of time spent drying, the method of measuring bacteria levels and other differences may account for the variation in results.
Identifying hygiene behaviours to help minimise the risk of cross-infection has become increasingly important. Much research has gone into the most effective hand washing techniques. The good news is that, whatever the limitations of the review, its findings support current hand washing recommendations.
This review suggests that paper towels are the best option for settings where containing infections is critical, and may be more effective than hot air dryers.
However, if you have no choice – as is the case in most public toilets and workplace washrooms – and only hot air dryers are provided, take extra time to dry your hands thoroughly. There is little evidence that they are any worse than hand towels, other than the extra time spent drying your hands.
There is some sensible advice for doctors on how they should wash their hands contained in NICE guidelines on infection control. You may want to make sure that your doctor or nurse knows about, and follows, this advice.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.