Dozens of studies have already shown that face masks are able to protect people from contracting or spreading the coronavirus, but new research is indicating that there is yet another potential benefit for mask-wearers—humidity created inside the mask can, in fact, fight off respiratory diseases like COVID-19. 

The study, led by researchers at the National Institutes of Health (NIH) and published in the Biophysical Journal, has found that face masks substantially increase the humidity in the air that a mask-wearer breathes in.  

This higher level of humidity—as it is known that hydration of the respiratory tract benefits the immune system—could help explain why wearing masks has been linked to lower severity in those infected with the coronavirus.  

“We found that face masks strongly increase the humidity in inhaled air and propose that the resulting hydration of the respiratory tract could be responsible for the documented finding that links lower COVID-19 disease severity to wearing a mask,” the study’s lead author Dr. Adriaan Bax, an NIH investigator, said in a statement.  

“High levels of humidity have been shown to mitigate severity of the flu, and it may be applicable to severity of COVID-19 through a similar mechanism.”

The researchers added that high levels of humidity can limit the spread of a virus to the lungs by promoting mucociliary clearance (MCC)—a defense mechanism that removes mucus and its potentially harmful particles from the lungs.

High levels of humidity also have been revealed to make the immune system more robust by producing special proteins called interferons that can fight off viruses. However, low levels of humidity have the potential to impair both MCC and the interferon response, which may be one reason why some individuals contract respiratory infections in cold weather.  

This particular study tested four common types of masks: an N95 mask, a three-ply disposable surgical mask, a two-ply cotton-polyester mask, and a heavy cotton mask. The results showed that all four masks raised the level of humidity of inhaled air, but to varying degrees. At lower temperatures, the humidifying effects of all masks vastly increased, and at all temperatures, the thick cotton mask led to the most increased level of humidity.

“The increased level of humidity is something most mask-wearers probably felt without being able to recognize, and without realizing that this humidity might actually be good for them,” Bax said.

The findings come after the U.S. Centers for Disease Control and Prevention recently confirming that double-masking, or the wearing of two face masks at once, can provide extremely high levels of protection against spreading and contracting the coronavirus.

The agency’s researchers said they explored the overall effectiveness of various masking approaches via laboratory experiments, which found that when an individual wears just one mask, either surgical or cloth, it blocked about 40 percent of the viral particles.  

However, wearing a cloth mask on top of a surgical mask was able to block about 80 percent of particles, while 95 percent was blocked when both individuals wore two masks, the researchers added.

Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters