It’s the cold season. Flu is lurking. And now there’s a coronavirus to worry about.

Maybe you've already seen several people walking around in face masks and considered getting one yourself.

The irony is that a face mask on YOU won’t do you much good.  But the face masks on THEM—meaning anyone else—might.

The usual paper face mask does a fairly good job of stopping contaminants like dust and tree pollen. So they are useful if you have seasonal allergies. Otherwise, not so much.

That’s because those standard loop-over-the-ear paper masks that cover your nose and mouth are moderately porous. They only block macroparticles—big ones that are 0.30 microns in diameter or larger. But viruses are microparticle, and they go right through the barrier. The recent coronavirus, first observed in Wuhan province, China, is only 0.12 microns in diameter.

There are two good things a paper mask accomplishes nonetheless. First of all, a mask may prevent you from touching your mouth and nose unthinkingly. Most often we don’t pick up cold and virus germs because someone sneezed right on us. We usually touch something with germs on it—like money, a chair back, or a countertop—then infect ourselves by touching our own mouth, nose, or eyes.  Researchers who watched a group of volunteers discovered that people touch their faces 23 times per hour on average.

The other big benefit of paper masks is that they can block your sneezes and sniffles from exploding outward to infect others.

But even if you are using a face mask for allergies, chances are good you are using it wrong. The biggest mistake is using the same mask over and over again. The masks themselves pick up contaminants and you transmit them to your nose and mouth when you put a previously used mask on your face.

You may be wondering why, if these masks are so ineffective, you see doctors and surgeons wearing them. Simple hygiene. They are not protecting themselves, however. They are protecting patients. A surgeon wears a mask for the same reason he washes his hands before operating.

If you want to protect yourself from flu and virus germs there are other ways. You could order an N95 mask, called a respirator. It’s much more expensive and has to be fitted carefully to be sure it stays tightly in place with normal head movement and that there are no leaks around the edges.

A better way to avoid germs, though, is to wash hands frequently, change and launder clothes daily, and stay as far from people with colds as possible.

As for the latest coronavirus, there is some good news, even if a mask won’t help. This virus is not as contagious as measles or as dangerous as SARS. Wash your hands well and often. Stay away from sick people and if you are sick, stay home.