Wearing medical masks can reduce the severity of COVID-19 in patients already infected with the coronavirus, according to scientists from the US National Institutes of Health.
The specialists have found that masks significantly increase the humidity of the inhaled air, thereby stimulating the production of interferons – proteins secreted by the body’s cells in response to a pathogen invasion.
“Increased moisture levels are something that most mask wearers probably felt without realizing that this moisture could actually be beneficial to them,” said Adriaan Bax, one of the study’s authors.
Humid air can also limit the virus’s spread to the lungs, promoting mucociliary clearance, a protective mechanism in the respiratory tract that removes mucus and potentially harmful particles from the lungs.
Scientists tested four common types of masks: No. 95, three-layer disposable surgical mask, two-layer cotton and polyester, and heavy cotton.
Volunteers were asked to breathe in an airtight black box, after which the moisture level in the box was measured. Then they repeated the procedure with a mask on their face. In the second case, the results showed that most of the water vapor remained on the tissue, condensed, and re-inhaled. The thickest cotton mask provided the highest level of moisture.