Hand hygiene

The most listening advice these days to avoid the spread of the coronavirus is that we have to wash our hands well. But why? To understand it we can resort to the Penfield homunculus, a representation of the human body proportional to the brain area that deals with sensory and motor functions. The eyes, tongue, lips, and especially the hands stand out. Most of the neural resources are spent daily on the hands. We eat, scratch, write, cook, dress, caress or tickle with our hands, hence the verb manipulate. In fact, it is one of the great achievements of our species. But everything has a price. If we observe the tip of a finger under a microscope, we will discover a real zoo. Fingerprints seem, on that scale, deep valleys in which all kinds of microorganisms (viruses, bacteria, fungi, and even worm eggs) can be housed. There are also epidermal cells that are scaling and the pores through which sweat is secreted. If instead of looking at the tip we look at the nail, we will be even more surprised. Despite the fact that we wash our hands often, several studies indicate that we do it incorrectly. We leave many areas uncleaned, especially between the fingers, under the nails and at the base of the thumb. Therefore, we have to scrub all these surfaces very well with soap for one minute. And soap is important for two reasons: because it removes fat from the fingers and allows water to drag microorganisms, but also because it dissolves the lipid bilayer that makes up the virus envelope.