Properly fitting, and properly filtering, face masks are an important part of medical personal protective equipment for keeping front line medical staff safe if they are in areas or situations of high viral load. (Or, indeed, in many other situations where they may be encountering any number of infectious agents.)
Otherwise, having a piece of paper or fabric in front of your mouth does almost nothing in keeping you from getting infected with the CoVID-19 virus.
The trouble is that, at the moment, and in the midst of a crisis, a lot of people, some authoritative but with specialized agendae, some not authoritative, and some merely visible and persuasive, are saying, on the basis of very limited evidence, that masks might be good for you, and, besides, what could it hurt?
Let's look at the (remarkably few) benefits, and the (much greater) risks. There are quite a number of reasons that it might hurt a lot.
The first is, what do you mean by "masks"? There are dust masks, that are intended to keep you from breathing in relatively large particles like sawdust. There are surgical masks, which look almost identical to dust masks, but are made differently and of different materials and to different standards, intended to keep you from breathing (or, more realistically, spitting) out droplets of who-knows-what over patients with open wounds. There are slightly form fitting masks made of specially porous materials that provide a larger surface to breath through and so filter smaller particles, droplets, and some aerosols out of the air you are breathing in. (These also tend to catch most droplets that you are breathing out, but probably not all, and not aerosols, since, when you breath out, your breath tends to push the mask away from your face, and allow your breath, aerosols, and some droplets to escape above, below, and to the sides of the mask. The same happens with dust and surgical masks.) Then there are extended form fitting respirators, many with integrated face or eye shields, and with filters to deal with specific particle sizes.
And then there are home made masks, fashioned from whatever fabric is to hand, to whatever design comes to mind, with little or no regard for porosity, size of weave, or the ability to trap whatever particles are being breathed in or out. Just last night, on the nightly news, the news anchor proudly showed off a face mask that his wife had crafted. It had a lovely pattern on the fabric, and was lined with plastic from a bag. Excuse me? Plastic? Non-breathable, non-porous plastic? I'm not sure what that is supposed to do. Any breathing is going to take place around the edges of the mask. A normal person, under no effort or stress, is probably not going to be harmed by it, but anybody with respiratory problems who uses it may be in serious difficulty. It may, almost accidentally, trap droplets that are breathed out, but otherwise I can't see any possible benefit at all.
The second major issue is the "evidence" for the benefit of masks. There seem to be two points of evidence.
The first piece of evidence is that nurses and medical techs wear masks. You can see them. They are the "face" of the medical system, and, these days, that face is covered with a mask. Obviously, masks are important.
"Obvious", as we say in mathematics, is what you say when you can't prove it. You do see nurses, medical techs, emergency first responders (on the news), and staff in intensive care units (on the news) wearing masks. You can't help but notice the masks. You don't notice gowns (changed between patients), gloves (changed between patients), face shields, and constant, everlasting hand-washing. You also don't see the vastly higher probabilities that these people will encounter the virus, nor the fact that the gowns (changed between patients), gloves (changed between patients), and masks (changed between patients) are intended as much to protect you as the medical staff. (Nor the "public relations" and "social engineering" aspects of "security theatre" intended to sooth fears in a time of poorly understood crisis. There are non-medical reasons to wear masks in some situations.)
The second piece of evidence is an "observation" (one cannot call it a study) that some populations with a high incidence of mask-wearing have significantly lower transmission rates of the virus. (You cannot call the observation a "study," since the sample size is very small. We are talking about whole countries (of which there are less than 200), and not just countries, but "countries with high rates of CoVID-19" which takes you down to a double handful. "A double handful" is not a statistically valid sample set.) There are two additional (and easily observable) factors that may affect the transmission rate without recourse to the idea that masks prevent infection. The first is that masks are, demonstrably, effective at reducing the probability that those who have the virus (and twenty-five to fifty percent of those who are infected show few or no symptoms and don't know they are infected) will directly pass the virus to others. (Masks, of pretty much any kind, tend to vastly reduce the droplets breathed or spit out by those infected, simply by trapping the droplets as they come into contact with the fabric or paper of the mask.) The second factor is that those countries with low transmission rates also have some pretty authoritarian governments, who can effectively and quickly mandate that people have to stay home and isolate themselves.
But, I hear you cry, while all of this calls into question the effectiveness of masks, it still doesn't show that masks (other than the plastic lined ones) are harmful. So, who's hurt if I choose to wear a mask?
Well, first off, we currently have a world-wide shortage of proper masks (and other medical equipment). If you are wearing a mask and don't need it, you may be (likely are) depriving some front line worker who may actually need it. In fact, if you have a proper mask these days, you probably got it on the black market, and you are, even if only in a small way, supporting criminal activity that extends up to massive theft of hospital supplies and the fraudulent production of "certified" medical equipment that is not up to anybody's standard. So you are probably hurting those doing the most to keep us safe. (And from there on down to legitimate manufacturers and the legitimate economy.)
And, even if you have made your own, probably ineffective, mask, you may be hurting yourself. We know that frequent, even obsessive, handwashing is effective. We know that physical distancing and self-isolation are effective. We know that keeping from touching your face is important. Wearing a mask gives you a feeling of security and safety. An almost certainly false sense of security and safety. And if wearing a mask makes you feel more comfortable and you stop, or even reduce, constant handwashing, or are less careful about physical distancing, or go out more frequently, you are putting yourself (and likely others) at greater risk. And we also know that properly donning and doffing a face mask is a non-trivial task, and most people don't know how to do it properly. (By the way, if you made your own mask, how many did you make? How often do you launder them? With bleach? (Where can you find bleach these days?) Do you change masks every time you go out? And do you touch your face when you put your mask on? Or take it off?)
With your own, homemade masks, you might be protecting others, but it's not likely. Yes, masks trap droplets, but that only matters if you are infected. Even if you live in Italy, there is only one chance in 600 that you have the virus. And if you know you are infected, wearing a mask does nothing if you are alone at home. If you are infected, you should be home alone. What are you doing going out if you are infected? Do you want to kill people?
Okay. You wanna wear a mask when you go out? During the virus crisis, if you must go out, note that you might get coughed on or sneezed on, and, since disinfecting fabric is much more difficult than cleaning flat surfaces, you should wear older clothing that can be discarded if necessary. (If you have old torn clothing that will not be missed, this is probably best.) Since face masks are in short supply, a scarf worn over the mouth, nose, and lower part of the face may offer some protection. If you are infected, and must go out for some reason, take a staff to aid you in walking, should you be overcome with respiratory distress and need something to lean on. Best to have bells hanging from the top to summon aid if needed. As you go, it is best to give some verbal warning to others not to come into close contact. Since some you may encounter may not be proficient in English, it is probably a good idea to constantly call out something simple, such as, "Unclean! Unclean!"
(This is not meant to make fun of anyone who actually has Hansen's Disease ...)
Masks are not magic. Since there is as-close-to-zero-as-makes-no-difference evidence that masks prevent normal people, in normal situations, from getting infected, those who believe that masks help obviously believe in magic. "Magical thinking" will not help us in this virus crisis. And it may do an awful lot of harm.
Now go wash your hands. (And, if you have any actual, medical grade masks, go and give them to a front line medical worker.)
We've been wearing masks in order to reduce the chance of droplet infection to others. It's the same reason medics use them; it's about protecting others rather than the wearer.
And just in case when you return home carefully remove the mask, surgical gloves and put them in the trash outside. They are single use after all. Enter your property, strip, put clothes in the wash and take a shower. It might seem OTT, but it's in line with what A&E staff and anaesthetists in our family are doing. But more generally I'm just avoiding direct contact with other people.
It might seem OTT, but it's in line with what A&E staff and anaesthetists in our family are doing.
The medical "professionals" in your family might want to seek advice from the infection control officers at their hospital. Contaminated medical gear should not be leaving treatment arena, much less staying on until they arrive home and given the severe shortages, decontamination is preferred over disposal.