What Is More Hygienic: Paper Towel Or Hand Dryer?
Whether flu, cold or gastrointestinal infection: Germs that cause illness are often transmitted via hands. This is why experts recommend frequent hand washing both in private households and in medical practices and hospitals. But how do you get your hands hygienically dry afterwards?
This question plays an important role for two reasons: On the one hand, microorganisms can multiply better on wet hands than on dry ones – that’s why drying hands after washing hands makes a lot of sense. On the other hand, it can sometimes happen that the number of germs on the hands increases when drying hands, for example with conventional towels made of fabric.
The reason is that cloth towels usually do not dry properly after use. The humid climate is an ideal breeding ground for germs. The next time the towel is used, the microorganisms are then easily passed on. For this reason, there are no longer any shared cloth towels in ordinary communal washrooms.
- 1 Paper or hot air?
- 2 Many bad studies …
- 3 … and no clear result
- 4 Test germs and everyday germs
- 5 Note other aspects when drying hands
- 6 Wash your hands properly
Paper or hot air?
Possible towel alternatives include paper towels or electric hand dryers.
There are two different modes of operation for dryers: hot air dryers, which heat the air and thus accelerate the evaporation of the water on the hands. And jet air dryers, which allow the air to circulate at room temperature at high speed, blowing water droplets from your hands.
We received the request of a reader who wants to re-equip the wash stations in his doctor’s office: Do paper towels or electric dryers ensure the cleanest hands?
Many bad studies …
In recent decades, this question has been repeatedly examined in studies. Our literature search revealed eight studies that addressed this issue. The studies considered different models of hot air dryers and paper towels; only one examined the relatively new jet air dryers. However, the studies differed considerably in their design.
The informative value was clearly limited in all studies, which was due to the concrete design, deficiencies in the implementation or evaluation.
… and no clear result
Because of the very different methods, it is not surprising that the studies come to very different results. In some studies, there were no significant differences between the drying methods, in others, however, electric dryers performed better.
However, there is also a study in which the results speak more for paper towels. In two of the studies, the number of bacteria on the hands even increased as a result of drying in some methods It is not clear whether this happens not only in the study laboratory, but also in everyday life, and what could be the reason for it.
Due to several shortcomings in the implementation, it is unclear whether some of these study results are more trustworthy than others. Based on the studies found, it is therefore not possible to decide whether paper towels or electric dryers ensure fewer germs on the hands.
Test germs and everyday germs
The researchers determined the number of microorganisms that remained on the hands after drying using very different methods, which makes it difficult to compare the results. Only four of the eight studies worked with those microorganisms that were naturally found on the hands of the test subjects. A test germ was used in the other half of the studies.
While this may be helpful for the repeatability of the study, it is questionable how well the laboratory results of these studies can be transferred to the everyday situation of most people.
Note other aspects when drying hands
In addition to the cleanliness of the hands, other factors also play a role in the specific decision “paper towels or electric dryer”. There are indications from studies that the jet air dryers, in particular, can distribute the water droplets very far in the washroom. If the hands were not really clean after washing, disease germs could also be spread further.
As a basic precautionary measure, the Robert Koch Institute, therefore, advises medical facilities against electric dryers and advocates the use of paper towels in dispensers, from which the towels can be removed individually without touching the other towels.
The choice of paper towels also avoids the problem that, depending on the model, electric dryers can lead to considerable noise pollution.
Wash your hands properly
By the way, studies that separately evaluated the effects of washing and drying came to the conclusion that washing has a greater influence on the microbial load on the hands than the drying method. Anyone who values good hand hygiene should, therefore, pay attention to the most important tips for handwashing :
- Wet your hands
- Use soap
- Do not only wash the palms of your hands and the back of your hands but also your fingertips, spaces between fingers, thumbs and fingernails
- Wash thoroughly: at least 20 to 30 seconds
- Rinse under running water
The studies in detail
The number of study participants was very low in almost all studies. An investigation was even carried out on only one person. There were 100 subjects in only one study. Four of the studies were sponsored by manufacturers of paper towels or electric dryers.
None of the scientific publications addressed the question of whether the remaining amount of germs on the hands would actually pose a relevant risk for the person himself or his surroundings. Possible infection risk can only be derived indirectly and very theoretically from the results.
Study on only one person hardly says anything
The investigations into the drying methods were very different. Most of the studies used methods that came very close to everyday situations: The test subjects washed their hands after contact with pathogens and then dried them.
However, one study had a single participant wet one finger with a test germ and then rinsed the contaminated area with various liquids using a small vial. This was followed by drying using one of the methods examined. Because of the very artificial experimental setup, we consider this study to be of little relevance to our question.
Studies with poor design cannot be compared
Only in four studies were the test subjects randomly assigned to a hand drying method. In most cases, the test subjects used different methods in succession (cross-over study). However, it was not evident from the publications whether the allocation was actually reliable and whether this procedure was adequately taken into account in the statistical evaluation.
If not, this would negate the advantage of random allocation, since it would not be clear whether the starting conditions when testing the different methods were actually comparable. For this reason, we do not consider the randomly assigned studies to be more reliable than the other studies.
The sometimes contradicting results can also be caused by the different techniques for determining the pathogens. Two studies determined the number of bacteria by placing the test subjects’ hands on a nutrient medium on which bacteria can multiply. In four studies, the germs were counted after wiping or rinsing the hands.
Two studies used both techniques, but at different points in the hand. In the majority of the studies, the hands were only tested for bacteria. The only one also examined the number of a particular virus responsible for gastrointestinal infections.
Missing “blinding” affects the result
Further methodological bias could also have resulted from the fact that both the participants and the evaluators knew who had used which drying method.
In fact, complete “blinding” of the studies is not possible: whether the hands are dried by a dryer or with a paper towel is clearly evident.
The evaluation of the germ load could very well have happened without the knowledge of the drying method. But only one study was so careful.
However, this would be very important: Because it is known from studies that knowledge of the method used can certainly influence the perception of the evaluators, for example, if they evaluate borderline findings on the nutrient media.