Masked Science: Do Masks Protect You From COVID-19?

Analysis by Dr. Joseph Mercola Fact Checked

do face masks prevent coronavirus

Story at-a-glance

  • Experts have been debating the effectiveness of wearing masks to reduce the risk of infection long before COVID-19 came into the picture, including those worn during surgery
  • Data show masks may not lower the risk of contracting the common cold and cloth masks increase the risk for health care workers of getting flu-like illnesses
  • The effectiveness of cloth masks reduced by 20% after being washed and dried four times. Wearing masks increases the potential for headaches and lowers a surgeon’s oxygen level
  • The WHO recommends several strategies to reduce the potential of infecting yourself, including proper handwashing before and after mask removal and replacing the mask as soon as it's damp


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

The COVID-19 pandemic has raised questions about the efficacy of wearing face masks to reduce the transmission of infectious disease. Health agencies are not always in agreement as to who should or should not be wearing masks. The World Health Organization currently states:1

“Medical masks should be worn by health workers and those caring for someone with COVID-19 symptoms, persons aged 60 and over and anyone with preexisting medical conditions as they are at greater risk of developing serious illness, and people who have symptoms suggestive of COVID-19.”

The Centers for Disease Control and Prevention clearly states that medical masks should be reserved for health care professionals and cloth masks should be worn by the public in areas where people congregate:2

“Cover your mouth and nose with a cloth face cover when around others. Do NOT use a facemask meant for a healthcare worker. Currently, surgical masks and N95 respirators are critical supplies that should be reserved for healthcare workers and other first responders.”

The CDC also states a cloth face mask will not prevent the wearer from getting sick but may keep the virus from spreading.3 Many medical and political leaders also support wearing masks in public, such as Dr. Anthony Fauci from the National Institute of Allergy and Infectious Diseases and past acting CDC director Dr. Richard Besser.4

Across the world, countries that have routinely embraced the use of face masks have posted lower numbers of COVID-19 transmissions.5 Whether this means the mask is reducing transmission or encouraging people to maintain social distancing are questions that still need to be answered.

What’s the Research Evidence for Wearing Masks?

Experts were debating the effectiveness of wearing masks to reduce the risk of infection long before COVID-19 came into the picture. Surgical masks were introduced nearly a century ago for the purpose of protecting patients during surgery. Yet, researchers continue to question whether this established routine is necessary.6

In one study published in 2016, scientists found no difference in the infection rates of patients undergoing “clean” surgery, whether the surgical team was masked or unmasked.7 A clean surgery was defined as one in which the lungs, gut, genitals and bladder were not involved.

Researchers have also questioned whether wearing masks during the cold season may cut down on the number of health care professionals who get sick.8 The researchers collected data for 77 consecutive days during cold season and determined whether a cold was present and if participants experienced symptoms based on their reports.

The intervention group wore masks at work and the control group did not. During the study period, one individual in the intervention and one in the control group got a cold. Although the study was small, the researchers felt there was not enough evidence to demonstrate benefits to health care workers in terms of preventing cold symptoms.

Investigations into the effectiveness of masks continued with a study published in BMJ.9 Since the results were released in 2015, the researchers have responded to their data in light of the COVID-19 pandemic. The study was aimed at comparing the effectiveness of cloth masks to that of medical masks in health care workers.

They evaluated 14 secondary and tertiary level hospitals in Hanoi, Vietnam, using 1,607 participants who worked full-time in high-risk units. Their measurement outcome was clinical demonstration of respiratory illness, flu-like illness or laboratory-confirmed respiratory infection.

The researchers found that those who wore cloth masks had a significantly higher rate of flu-like illness and all measured infections as compared to participants using medical masks. They cited moisture retention, reuse and poor filtration as potential reasons for the increased rates of infection.

They wrote, “… cloth masks should not be recommended for HCWs [health care workers], particularly in high-risk situations, and guidelines need to be updated.”10

How Do Cloth Masks Stack Up?

In follow-up comments published in March 2020, the researchers pointed to critical shortages of personal protective equipment and stated that while those wearing cloth masks have a higher rate of infection, they may be better for health care workers than wearing no mask at all.11 They went on to say their research does not excuse health care workers from working unprotected.

Just prior to the pandemic reaching the U.S., a team evaluated the effectiveness of low-cost cloth face masks. The study was published in 2019 and was undertaken since these materials are commonly used in developing countries.12 The team evaluated 20 types of cloth masks and found pore size could range from 80 to 500 nanometers.

This is significantly larger than particulate matter with a diameter of 10 nanometers or less (PM10). They also found that the effectiveness was reduced by 20% after the mask had gone through the fourth cycle of washing and drying. Stretching of the surface altered pore size and washing reduced the number of microfibers within the pores, also altering the effectiveness of the mask.

Finally, the authors of a recently-released preprint study evaluated the effectiveness of reducing airflow in face covers with and without an outlet valve.13 The researchers measured airflow from a person during quiet and heavy breathing and coughing while using different types of face covers.

They found that face covers without an outlet valve reduced the flow of air forward by more than 90%. Individuals using surgical, cloth masks and face shields had intense back and downward flow, which may present a hazard.

What Risks Do Masks Carry for the Wearer?

In the study from Asia in which the symptoms of health care workers who wore face masks were compared to those who did not, researchers asked about headaches, among other things. Participants who wore masks were much more likely to complain of headaches than those who did not wear masks.14

In a more recent study published in the journal Headache, researchers sought to evaluate the factors associated with headaches resulting from the use of personal protection equipment.15

They also wanted to look into workers’ thoughts on how headaches affected their health and performance. The study team surveyed clinicians at a tertiary care hospital where they worked in areas taking care of COVID-19 patients.

Data were gathered from 158 health care workers including nurses, doctors and paramedical staff. During the study, 128 developed headaches associated with their personal protection equipment and 91.3%:16

“… of respondents with pre‐existing headache diagnosis either ‘agreed’ or ‘strongly agreed’ that the increased PPE usage had affected the control of their background headaches, which affected their level of work performance.”

The researchers did not question the origin of the headaches in the participants, but others have asked whether wearing a mask could reduce levels of oxygen or raise CO2 levels, which in turn could produce a headache.

Surgeons Experience Lower Oxygen Saturation

This question was asked in 2008 by a team of researchers from Turkey who evaluated the oxygen saturation of 53 surgeons during surgical procedures.17 The team used a pulse oximeter before the procedure and immediately postoperatively. The results showed the surgeons experienced a decrease in oxygen saturation and a slight increase in pulse rate.

The decrease in oxygen saturation was more significant in surgeons over the age of 35. Due to the design of the study, the researchers were unable to determine whether the changes in oxygen saturation were from the face mask or stress during the surgery. Concerned about the consistent use of face masks, retired neurosurgeon Dr. Russell Blaylock warned that face masks:18

“… fail to protect the healthy from getting sick, but they also create serious health risks to the wearer. The bottom line is that if you are not sick, you should not wear a face mask.”

He expressed some frustration at the wholesale use of face masks for the vulnerable and healthy individuals, pointing out, “When a person has TB we have them wear a mask, not the entire community of noninfected.”

He referenced a study in 2006 in which researchers evaluated the development of headaches in health care workers who were using an N95 face mask.19 Using a survey, they found that 37.3% reported mask-associated headaches and 32.9% said that this happened more than six times per month.

During the study, 59.5% used analgesics for headache pain and 2.1% took preventive medications. The researchers concluded that the N95 face mask could increase the risk of headaches in health care providers and that using them for shorter periods of time could reduce the frequency and severity of their headaches.

Wearing an N95 mask for up to three hours could have also changed nasal function, making it more difficult to breathe after the mask was removed.20 Before Blaylock went on to discuss the new evidence suggesting coronaviruses may enter the brain, he pointed out:21

“There is another danger to wearing these masks on a daily basis, especially if worn for several hours. When a person is infected with a respiratory virus, they will expel some of the virus with each breath.

If they are wearing a mask, especially an N95 mask or other tightly fitting mask, they will be constantly rebreathing the viruses, raising the concentration of the virus in the lungs and the nasal passages. We know that people who have the worst reactions to the coronavirus have the highest concentrations of the virus early on.”

Neurological Infections May Enter Through the Nose

Based on past evidence,22 Blaylock questions whether wearing a mask could also reintroduce exhaled viruses deep into the nasal cavity, driving up the amount of virus in the upper respiratory tract and increasing the potential to enter the olfactory nerves and travel into the brain.23

Blaylock is not the only expert to react to the widespread use of masks. One group of experts writing in the New England Journal of Medicine said:24

“We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes).

The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.”

They go on to describe why masks may be critical to protect health care workers in close proximity to patients with active and symptomatic COVID-19. For those working in close quarters with health care workers who may be asymptomatic or who have a mild disease, a mask may at least lessen the risk for patients and other employees to get sick.

The authors of a paper published in the Journal of the American Medical Association agree that face masks should only be used by “individuals who have symptoms of respiratory infection such as coughing, sneezing, or, in some cases, fever.”25 The authors go on to say there's no evidence masks used by healthy people can prevent others from becoming sick.

If You Wear a Mask Use These Guidelines

Ultimately, the goal is to reduce transmission of infectious disease, including COVID-19. It’s apparent scientific evidence supporting or debunking face masks is far from conclusive. If you do choose to wear a face mask, here are strategies from the WHO for reducing the potential of infecting yourself:26

  • Before putting on a mask, clean your hands with soap and water.
  • Cover your mouth and nose with the mask and make sure there are no gaps between your face and the mask.
  • Avoid touching the mask while using it; if you have to, try to clean your hands with alcohol-based hand rub or soap and water before doing so.
  • Replace the mask with a new one as soon as it is damp. Do not reuse single-use masks.
  • To take off the mask: Remove it from behind (do not touch the front of the mask); discard it immediately in a closed bin; and clean your hands with alcohol-based hand rub or soap and water.


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