Dear Alice,

What the heck is the deal with people in Japan wearing surgical masks? Where I come from (Canada), only doctors, dentists and other health professionals wear masks, and only on the job. You never see anyone out in public wearing a face mask. In fact, if you tried to enter a store with one on your face, you'd be mistaken for a robber and someone would call the police. Yet here in Japan, it's not at all unusual to see people out and about wearing masks. And it could be my imagination, but I get the feeling they've become even more common in recent years. I'd like to know whether these masks are effective. Do Japanese catch fewer colds?

Allan M., Tokyo

Dear Allan,

It's not your imagination. There's definitely been an increase in the number of Japanese wearing face masks, and as more consumers seek them out, the once-humble mask has moved from the back aisles to more prominent placement in retail stores. And as we move into the cold, flu and hay fever seasons, the displays seem to get bigger every day.

To get a peek behind the mask market, I paid a visit to the Tokyo headquarters of Unicharm Corporation, a major manufacturer and the first company to offer the popular rittai (3-D) masks that stand away from the face. Brand manager Naoe Hirooka walked me through the market and brought me up to date on consumer trends.

First, let's look at product types. While some elderly consumers still use cloth gauze masks that can be laundered and reused, almost the entire market is now made up of tsukaisute (disposable) masks made of nonwoven cloth, which is called fushokufu in Japanese. The most standard style is the purītsu-(pleats) type mask, which can be adjusted to fit around the chin, but 3-D masks have steadily gained market share since Unicharm first introduced them in 2003. The main advantage of 3-D masks is that they fit closer, with fewer gaps, yet provide a space between the mask and the mouth that makes it easier to breathe. They are also less likely to muss up makeup, making them popular with women.

According to the Japan Hygiene Products Association, the earliest commercial face masks in Japan were cloth stretched over metal frames that were tied to the face as air filters for factory workers. But the general public picked them up in response to the Spanish influenza pandemic in 1918. Sales spiked again during another flu outbreak in 1938 and pretty much every outbreak after that. The frameless, soft masks that were the precursor of the types we see today came on the market about 1948.

In the postwar period and until recently, the typical mask wearer was someone who had a cold and didn't want to infect others. They would put the mask on in crowded situations, such as when riding the morning train, out of consideration to those around them. But they'd take it off as soon as possible because they felt embarrassed to be seen with a mask on.

But recently there's been a shift in consumer attitudes. "The percentage of respondents in our surveys who said they don't like to wear a mask because 'others might think they are sick' (byōnin ni miraresō) dropped by two-thirds between 2008 and 2014," Hirooka reported. Those who said wearing a mask is "embarrassing" (hazukashii) dropped even more precipitously. "More and more, wearing a mask is seen as normal in Japan," Hirooka observed.

The turning point seems to have been 2009, when once again the country was in a panic over influenza, this time the H1N1 strain, which was popularly known as the "swine flu." "All of a sudden, everyone was wearing a mask, so no one felt embarrassed," Hirooka recalled. "That event went a long way in creating anacceptance for wearing masks in public."

Now, far from being self-conscious, there is even a cadre of healthy users who wear masks because they think it makes them more attractive, supposedly by emphasizing the eyes, creating an illusion of better skin color or just lending an air of mystery. This usage is called date masuku — "date," pronounced "dah-teh," means "just for show." Others, including celebrities and women who want to run to the convenience store without bothering with makeup, wear masks to hide from public view. There are also consumers who use masks to create a psychological barrier against the rest of the world, either because they are shy, antisocial or simply want to concentrate.

"A number of people have told us a mask helps them focus for study or work," Hirooka told me.

Given this diversification in motivation, it's hard to address your query on efficacy. I mean, "Effective for what?" But having a cold is still the top reason people give for wearing masks, so let's start there.

If anyone has come up with reliable statistics that compare the rate of cold-catching in different countries, I couldn't find them. But I can report that a mask, when worn properly, provides some protection against the respiratory droplets that fly into the air when an infected person coughs or sneezes. Masks also help prevent colds by maintaining moisture in the mouth, nose and throat. Mucous membranes there are covered with tiny hairs that move viruses and bacteria out of the body, but in dry conditions the movement of the hairs slow and become less effective.

Many people swear by masks for reducing their exposure to pollen and relieving hay fever symptoms, and new research indicates that masks may also prove helpful to asthma sufferers. In a study reported by Japanese doctors last year at a medical conference in the United States, children with asthma who wore masks at night suffered fewer attacks, presumably because the masks cut down the amount of house dust they inhaled from bedding.

And when it comes to preventing the flu, masks come widely recommended. Government agencies in Japan urge mask use, along with frequent hand-washing and covering the face when sneezing, to fight influenza infection. Many schools, too, ask students to come to school with masks. In a study conducted in 2009 at Ogumiyamae Elementary School in Arakawa Ward, Tokyo, 9.7 percent of students who didn't wear masks (10 out of 103) contracted influenza, compared to 2 percent (3 out of 151) of the students who wore masks.

Now, that's nothing to sneeze at.