https://www.nih.gov/news-events/news-releases/researchers-propose-humidity-masks-may-lessen-severity-covid-19 Skip to main content * U.S. Department of Health & Human Services National Institutes of Health (NIH) - Turning Discovery into Health Search the NIH Website [ ][Search] * NIH Employee Intranet * Staff Directory * En Espanol Site Menu * Home * Health Information + Health Info Lines + Find Health Services + HealthCare.gov + NIH Clinical Research Trials and You + Talking to Your Doctor + Science Education Resources + Community Resources + Clear Health A-Z + Publications List More >> Search Health Topics [ ] [Go] Quick Links + MedlinePlus Health Info + NIH News in Health + Wellness Toolkits * Grants & Funding + Grants Home Page + Find Funding + Due Dates + How to Apply + About Grants + Policy & Compliance + Grants News/Blog + Contracts + Loan Repayment More >> Search the NIH Guide [ ] [Go] Quick Links + RePORT + eRA Commons + NIH Common Fund * News & Events + News Releases + Digital Media Kits + Media Resources + Media Contacts + Images and B-roll + Events + Social Media More >> Quick Links + NIH News in Health + NIH Research Matters + NIH Record * Research & Training + Medical Research Initiatives + Science Highlights + Science Education + Research in NIH Labs & Clinics + Training Opportunities + Library Resources + Research Resources + Clinical Research Resources + Safety, Regulation and Guidance More >> Quick Links + PubMed + Stem Cell Information + OppNet + NIDB + NIH Blueprint for Neuroscience Research * Institutes at NIH + List of Institutes, Centers & Offices + NIH Office of the Director + Directors of NIH Institutes and Centers + NIH Institute and Center Contact Information More >> Quick Links + NCI + NEI + NHLBI + NHGRI + NIA + NIAAA + NIAID + NIAMS + NIBIB + NICHD + NIDCD + NIDCR + NIDDK + NIDA + NIEHS + NIGMS + NIMH + NIMHD + NINDS + NINR + NLM + CC + CIT + CSR + FIC + NCATS + NCCIH + OD * About NIH + Who We Are + What We Do + Jobs at NIH + Visitor Information + Frequently Asked Questions + Contact Us More >> Quick Links + The NIH Director + The NIH Almanac + NIH...Turning Discovery Into Health^(r) + Impact of NIH Research + Science, Health, and Public Trust COVID-19 is an emerging, rapidly evolving situation. * Get the latest public health information from CDC >> * Get the latest research information from NIH >> * NIH staff guidance on coronavirus (NIH Only) >> You are here Home >> News & Events >> News Releases News Releases News Release Friday, February 12, 2021 Researchers propose that humidity from masks may lessen severity of COVID-19 NIH study compares how different face masks affect humidity inside the mask. Study volunteer breathes into box while wearing mask NIDDK's Dr. Joseph Courtney breathes into sealed box while wearing a maskNIDDK Masks help protect the people wearing them from getting or spreading SARS-CoV-2, the virus that causes COVID-19, but now researchers from the National Institutes of Health have added evidence for yet another potential benefit for wearers: The humidity created inside the mask may help combat respiratory diseases such as COVID-19. The study, led by researchers in the NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), found that face masks substantially increase the humidity in the air that the mask-wearer breathes in. This higher level of humidity in inhaled air, the researchers suggest, could help explain why wearing masks has been linked to lower disease severity in people infected with SARS-CoV-2, because hydration of the respiratory tract is known to benefit the immune system. The study published in the Biophysical Journal. "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," said the study's lead author, Adriaan Bax, Ph.D., NIH Distinguished Investigator. "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." Researcher sits in his labDr. Adriaan Bax sits in front of lab equipment.NIDDK 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 potentially harmful particles within the mucus - from the lungs. High levels of humidity can also bolster the immune system by producing special proteins, called interferons, that fight against viruses - a process known as the interferon response. Low levels of humidity have been shown to impair both MCC and the interferon response, which may be one reason why people are likelier to get respiratory infections in cold weather. The 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 researchers measured the level of humidity by having a volunteer breathe into a sealed steel box. When the person wore no mask, the water vapor of the exhaled breath filled the box, leading to a rapid increase in humidity inside the box. When the person wore a mask, the buildup of humidity inside the box greatly decreased, due to most of the water vapor remaining in the mask, becoming condensed, and being re-inhaled. To ensure no leakage, the masks were tightly fitted against the volunteer's face using high-density foam rubber. Measurements were taken at three different air temperatures, ranging from about 46 to 98 degrees Fahrenheit. The results showed that all four masks increased the level of humidity of inhaled air, but to varying degrees. At lower temperatures, the humidifying effects of all masks greatly increased. 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 researchers did not look at which masks are most effective against inhalation or transmission of the virus and defer to the CDC for guidance on choosing a mask. Earlier studies from Bax and his colleagues showed that any cloth mask can help block the thousands of saliva droplets that people release through simple speech - droplets that, if released, can remain in the air for many minutes. While the current study did not examine respiratory droplets, it does offer more evidence as to why masks are essential to battling COVID-19. "Even as more people nationwide begin to get vaccinated, we must remain vigilant about doing our part to prevent the spread of the coronavirus that causes COVID-19," said NIDDK Director Dr. Griffin P. Rodgers. "This research supports the importance of mask-wearing as a simple, yet effective, way to protect the people around us and to protect ourselves from respiratory infection, especially during these winter months when susceptibility to these viruses increases." The research was supported by the NIDDK Intramural Research Program and the NIH Intramural Antiviral Target Program. About the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): The NIDDK, a component of the National Institutes of Health (NIH), conducts and supports research on diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition and obesity; and kidney, urologic and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe, and disabling conditions affecting Americans. For more information about the NIDDK and its programs, see http:// www.niddk.nih.gov. About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov. NIH...Turning Discovery Into Health^(r) References Courtney, JM and Bax, A. Hydrating the respiratory tract: An alternative explanation why masks lower severity of COVID-19 disease. Biophysical Journal. February 11, 2021. ### Institute/Center National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Contact Lisa Yuan 301-496-3583 Connect with Us * Subscribe to news releases * RSS Feed Connect with Us * Contact Us * Twitter * Facebook * Instagram * YouTube * Flickr * More Social Media from NIH Footer * NIH Home * En Espanol * Site Map * Visitor Information * Frequently Asked Questions * Web Policies and Notices * Freedom of Information Act * No Fear Act * Office of Inspector General * USA.gov - Government Made Easy NIH...Turning Discovery Into Health^(r) National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892 U.S. Department of Health and Human Services Back to Top