In recent days, the experiment of a user who made visible the amount of bacteria that grow under a hand dryer of hot air, like the ones in public toilets. For this, he used petri disheswhich are those plastic plates with substances on which microbes are planted and allowed to proliferate in the laboratory.
It is not the first time that this topic has been discussed. In fact, there are many scientific studies dedicated to comparing the microbial proliferation derived from the different ways of drying hands. Normally, the use of paper towels with the use of hand dryers. Although other variables can also be introduced, such as drying them on the clothes themselves or in the air. In this TikTok video they compare dryers to something as simple as shake hands.
The result leaves hand dryers in a very bad place, as do some scientific studies. But to what extent should we flee from these devices? can we consider them dangerous? The answer is not as simple as yes or no, as it depends on many factors.
This is how hand dryers work
Broadly speaking, hand dryers contain an electrical resistance and a fan, formed by an impeller and an electric motor. When it is connected to the current, the temperature of the resistance rises, which begins to generate heat. But, in addition, the motor turns the impeller, which releases a jet of air that is heated by the effect of resistance.
There are some hand dryers that only blow up one of the parts, so they can be divided into devices jet or hot air. Whatever type they are, they all have a fairly negative reputation about their relationship with microbial proliferation. For this reason, many studies have been published in this regard in recent years.
Is the TikTok video right?
When evaluating both the results of the TikTok experiment and all those scientific studies, it is necessary to differentiate between the environmental bacteria and those that were previously in the hands.
What is clear is that most microbes take advantage of moisture to proliferate, so it is important to dry your hands well after washing them. Whatever method it is.
Bearing this in mind, we can differentiate between different drying methods. In a study published in 2019, drying was compared on clothes, with a paper towel, with two paper towels, with a hot air dryer for 20 seconds, with hands stationary or rubbed together, and with the hot air dryer until hands are completely dry.
In this case Bacteria on hands were measured before and after drying and it was observed that the best method to eliminate them is with hand dryers, without rubbing them together. Another interesting fact that emerges from this study is that there is no difference between using one or two paper towels, so better for the environmentIf you prefer to avoid hand dryers, use only one.
But what about the microorganisms that remain in the air? That is another question. In 2014, a study was carried out in which levels of microbial contamination in the surrounding air were measured after hand drying with hot air dryers, jet dryers or paper towels. Volunteers had lactobacilli put on their skin to simulate poorly washed hands, so some contamination was expected. But this was much higher with hand dryers, especially jet dryers.
Perhaps this in environments where there is not supposed to be an abundance of sick people would not be a problem. It would be the case of a bar, for example. However, the study concludes that in places like the hospitals yes, these drying methods should be avoided.
On the other hand, it should be noted that the most recent reviews of the scientific literature maintain that no solid evidence to discourage hand dryers. Yes, the greater innocuousness of paper towels is pointed out. However, there is no talk of clear evidence against drying machines.
It is for this reason that, outside the hospital setting, it shouldn’t be a problem to use these machines. Although it is clear that paper towels are a safe option that enjoys much more evidence.
Now, what about the TikTok video? The results are frightening, but, beyond the anecdotal, cannot be compared with a scientific study with well-designed conditions. Also, the comparison is to shaking hands, not even talking about paper towels. Shaking your hands usually means leaving them wet and that is a bad idea if we want to avoid microbial proliferation. It’s a TikTok viral, no more. What counts is interesting, but we shouldn’t obsess over the results either.