A Digest of the Data and Scientific Evidence of Masks, Mask Mandates, and Mask Recommendations

MaskScience.org links to 42 high-impact, peer-reviewed studies illustrating why masks fail to curb or reduce the community spread of Covid-19 or other contagious viruses, the negative effects of masking, and the adverse effects on children. This site includes links to numerous randomized clinical trials (RCTs) that evaluated the effects of masking on the airborne transmission of pathogens, including SARS-CoV-2. RCTs are the “gold standard” for measuring the effectiveness of an intervention. Several observational studies are not included on this site for the reasons well articulated in the August 2021 meta-analysis, Do Masks Work? This site is an actively maintained project. New studies are added as they become available. Suggestions are welcome by email. Help spread the word about this site.


Studies on Masks Expert Commentary Mask Charts Negative Effects Children & Masks Disclosures


Studies on Masks

Peer Reviewed Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers

Peer Reviewed A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

Peer Reviewed N95 Respirators vs. Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

Peer Reviewed Physical interventions to interrupt or reduce the spread of respiratory viruses

Peer Reviewed Do facemasks protect against COVID-19?

Peer Reviewed Optical microscopic study of surface morphology and filtering efficiency of face masks

Peer Reviewed Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk

Peer Reviewed Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles

Peer Reviewed Comparison of Filtration Efficiency and Pressure Drop in Anti-Yellow Sand Masks, Quarantine Masks, Medical Masks, General Masks, and Handkerchiefs

Peer Reviewed Experimental investigation of indoor aerosol dispersion and accumulation in the context of COVID-19: Effects of masks and ventilation

Peer Reviewed Universal Masking in Hospitals in the Covid-19 Era

Peer Reviewed Disposable surgical face masks for preventing surgical wound infection in clean surgery

Peer Reviewed Face seal leakage of half masks and surgical masks

Peer Reviewed Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

Peer Reviewed Aerosol penetration through surgical masks

Peer Reviewed Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial

Peer Reviewed Face masks to prevent transmission of influenza virus: a systematic review.

Peer Reviewed The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence

Peer Reviewed Aerosol penetration and leakage characteristics of masks used in the health care industry.

Peer Reviewed Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures

Peer Reviewed Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza

Peer Reviewed The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence

Peer Reviewed Surgical Mask to Prevent Influenza Transmission in Households: A Cluster Randomized Trial

Peer Reviewed Is a Mask Necessary in the Operating Theatre?

Peer Reviewed Postoperative wound infections and surgical face masks: a controlled study

Peer Reviewed An Experimental Study of the Efficacy of Gauze Face Masks

Peer Reviewed Analysis of the Effects of COVID-19 Mask Mandates on Hospital Resource Consumption and Mortality at the County Level

Peer Reviewed Contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers

Low-cost measurement of face mask efficacy for filtering expelled droplets during speech

Aerosol filtering efficiency of respiratory face masks used during the COVID-19 pandemic

Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review

Evidence for Community Cloth Face Masking to Limit the Spread of SARS‐​CoV‑2: A Critical Review

 

Expert Commentary

A Virologist and WHO to Clarify: The Mouth-Nose Protection can be a breeding ground for many germs

Why is Sweden not recommending face masks to the public?

Are Face Masks Effective? The Evidence (Swiss Policy Research)

Do face masks work? A note on the evidence

Is Routine Use of a Face Mask Necessary in the Operating Room?

Standard Surgical Masks Do Not Protect Wearer From Getting Swine Flu

European Centre for Disease Prevention and Control

World Health Organization

Mask Charts

Peer Reviewed Mask mandate and use efficacy for COVID-19 containment in US States

Unmasked: Mask Charts from Ian Miller

COVID-19 Mitigation Practices and COVID-19 Rates in Schools: Report on Data from Florida, New York and Massachusetts

Mask mandate and use efficacy in state-level COVID-19 containment


Negative Effects

Peer Reviewed Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?

Peer Reviewed Effect of a surgical mask on six minute walking distance

Peer Reviewed Effect of facemasks on empathy and relational continuity: a randomised controlled trial in primary care

Peer Reviewed “Exercise with facemask; Are we handling a devil's sword?” - A physiological hypothesis

Peer Reviewed Mask use during high impact exercise in the pandemic

Peer Reviewed Respiratory consequences of N95-type Mask usage in pregnant healthcare workers—a controlled clinical study

Peer Reviewed Headaches Associated With Personal Protective Equipment – A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19

Peer Reviewed Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations

Peer Reviewed Use of face mask by blood donors during the COVID-19 pandemic: Impact on donor hemoglobin concentration: A bane or a boon

Peer Reviewed A Study on the Effect of Wearing Masks on Stress Response

Chemical cocktail found in face masks

 

Children and Masks

Peer Reviewed Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?

Peer Reviewed Masking Emotions: Face Masks Impair How We Read Emotions

Association between School Mask Mandates and SARS-CoV-2 Student Infections: Evidence from a Natural Experiment of Neighboring K-12 Districts in North Dakota

Impact of the COVID-19 Pandemic on Early Child Cognitive Development: Initial Findings in a Longitudinal Observational Study of Child Health

Dangerous pathogens found on children’s face masks

Mandatory masks in school are a ‘major threat’ to children’s development, doctors warn

Doctors want coronavirus measures for under-12s in schools to be dropped

The Londoner: Let children be exposed to viruses, says Professor Gupta

The Science of Masking Kids at School Remains Uncertain

COVID-19 School Response Dashboard

School masks: face coverings could damage children's speech development, warn scientists

Making pre-school children wear masks is bad public health

The Case Against Masks for Children

 



Studies on Masks

Peer Reviewed Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers

This is the only peer-reviewed, controlled study completed on COVID-19 and masks worn in the community. It was published in November 2020, and it shows that masks are not effective at protecting the wearer.

“[A] recommendation to wear a surgical mask when outside the home among others did not reduce, at conventional levels of statistical significance, incident SARS-CoV-2 infection compared with no mask recommendation.”

Peer Reviewed A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

“This study is the first RCT of cloth masks, and the results caution against the use of cloth masks…. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.”

Peer Reviewed N95 Respirators vs. Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

“N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.”

Peer Reviewed Physical interventions to interrupt or reduce the spread of respiratory viruses

“We included 44 new RCTs and cluster-RCTs in this update, bringing the total number of randomised trials to 67.... There is uncertainty about the effects of face masks.... The pooled results of randomised trials did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks during seasonal influenza. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection.... Harms associated with physical interventions were under-investigated.”

“There is moderate certainty evidence that wearing a mask probably makes little or no difference to the outcome of laboratory‐confirmed influenza compared to not wearing a mask....”

Peer Reviewed Do facemasks protect against COVID-19?

“Thus, a pre-symptomatic or mildly infected person wearing a facemask for hours without changing it and without washing hands every time they touched the mask could paradoxically increase the risk of infecting others.”

Peer Reviewed Optical microscopic study of surface morphology and filtering efficiency of face masks

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This was a study of the efficiency of cloth masks over time. Cloth masks are the kind the government says we must wear. Medical masks should be saved for first responders.

“The poor filtering efficiency may have arisen from larger and open pores present in the masks. Interestingly, we found that efficiency dropped by 20% after the 4th washing and drying cycle. We observed a change in pore size and shape and a decrease in microfibers within the pores after washing. Stretching of [cloth mask] surface also altered the pore size and potentially decreased the filtering efficiency.”

“The findings of this study suggest that [cloth masks] are not effective, and that effectiveness deteriorates if used after washing and drying cycles and if used under stretched condition.”

Peer Reviewed Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk 

This study notes what happens to the leakage that comes out the sides of masks, especially when those masks aren’t fitted properly. Instead of lighter, dispersed airflow in front of your face, strong jet streams go out the side and over the top of your mask, creating a risk for people around you.

From the Overview: “Surgical and hand-made masks, and face shields, generate several leakage jets, including intense backward and downwards jets that may present major hazards.”

“Surgical and handmade masks, and face shields, generate significant leakage jets that have the potential to disperse virus-laden fluid particles by several metres. The different nature of the masks and shields makes the direction of these jets difficult to predict, but the directionality of these jets should be a main design consideration for these covers. They all showed an intense backward airflow for heavy breathing and coughing conditions. It is important to be aware of this flow, to avoid a false sense of security that may arise when standing to the side of, or behind, a person wearing a surgical, or handmade mask, or shield. This is of relevance given the potential for some wearers of surgical masks to turn their face to the side when they cough, during face-to-face interactions with a colleague. In doing so, our data show that there is a risk that this backward jet is directed closer to a person standing in front of the wearer. Additionally, clinicians working around a patient, in the confined space around an intensive care bed or an operating table, are likely to be exposed to these side and backward leakage jets from surgical masks worn by colleagues.”

Peer Reviewed Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles

“The results obtained in the study showed that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels when challenged with polydisperse NaCl aerosols . . . . A poor filtration performance is expected for improvised fabric materials because these materials are not designed for respiratory protection.”

Peer Reviewed Comparison of Filtration Efficiency and Pressure Drop in Anti-Yellow Sand Masks, Quarantine Masks, Medical Masks, General Masks, and Handkerchiefs

“General masks and handkerchiefs have no protection function in terms of the aerosol filtration efficiency.”

“Medical masks, general masks, and handkerchiefs were found to provide little protection against respiratory aerosols.”

Peer Reviewed Experimental investigation of indoor aerosol dispersion and accumulation in the context of COVID-19: Effects of masks and ventilation

“The results show that a standard surgical and three-ply cloth masks, which see current widespread use, filter at apparent efficiencies of only 12.4% and 9.8%, respectively. Apparent efficiencies of 46.3% and 60.2% are found for KN95 and R95 masks, respectively, which are still notably lower than the verified 95% rated ideal efficiencies. Furthermore, the efficiencies of a loose-fitting KN95 and a KN95 mask equipped with a one-way valve were evaluated, showing that a one-way valve reduces the mask's apparent efficiency by more than half (down to 20.3%), while a loose-fitting KN95 provides a negligible apparent filtration efficiency (3.4%).”

Peer Reviewed Universal Masking in Hospitals in the Covid-19 Era

"We know that wearing a mask outside health care facilities offers little, if any, protection from infection. . . . the desire for widespread masking is a reflexive reaction to anxiety over the pandemic."

But then, in an interesting twist, the study concludes that the usefulness of universal masking even in a hospital is limited and that the biggest benefit is psychological. (Note: They are addressing the staff that isn't directly responsible for COVID patients.)

“A mask alone will not prevent health care workers with early Covid-19 from contaminating their hands and spreading the virus to patients and colleagues. Focusing on universal masking alone may, paradoxically, lead to more transmission of Covid-19 if it diverts attention from implementing more fundamental infection-control measures. . . . [Masks are] talismans that may help increase health care workers’ perceived sense of safety, well-being, and trust in their hospitals.”

Peer Reviewed Disposable surgical face masks for preventing surgical wound infection in clean surgery

“There was no statistically significant difference in infection rates between the masked and unmasked group in any of the trials.”

“From the limited results it is unclear whether the wearing of surgical face masks by members of the surgical team has any impact on surgical wound infection rates for patients undergoing clean surgery.”

Peer Reviewed Face seal leakage of half masks and surgical masks

“Filtration and leakage were studied as a function of particle size over a diameter range of 0.3-10 micron.... The filtration efficiency of the filter materials was good, over 95%, for particles above 5 micron in diameter but great variation existed for smaller particles.”

Peer Reviewed Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

“Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed).” (Emphasis added.)

Peer Reviewed Aerosol penetration through surgical masks

“Although surgical mask media may be adequate to remove bacteria exhaled or expelled by health care workers, they may not be sufficient to remove the submicrometer-size aerosols containing pathogens to which these health care workers are potentially exposed.”

Peer Reviewed Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial

“Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds.”

Peer Reviewed Face masks to prevent transmission of influenza virus: a systematic review

“While there is some experimental evidence that masks should be able to reduce infectiousness under controlled conditions, there is less evidence on whether this translates to effectiveness in natural settings. There is little evidence to support the effectiveness of face masks to reduce the risk of infection.”

Peer Reviewed The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence

 “None of the studies we reviewed established a conclusive relationship between mask/respirator use and protection against influenza infection.”

“In conclusion, there is a limited evidence base to support the use of masks and/or respirators in healthcare or community settings.”

Peer Reviewed Aerosol penetration and leakage characteristics of masks used in the health care industry

“We conclude that the protection provided by surgical masks may be insufficient in environments containing potentially hazardous submicrometer-sized aerosols.”

Peer Reviewed Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures

“We found no significant reduction in influenza transmission with the use of face masks.”

Peer Reviewed Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza

“Ten RCTs were included in meta-analysis, and there was no evidence that face masks are effective in reducing transmission of laboratory-confirmed influenza.”

Peer Reviewed The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence

“None of the studies we reviewed established a conclusive relationship between mask/respirator use and protection against influenza infection. 

“In conclusion, there is a limited evidence base to support the use of masks and/or respirators in healthcare or community settings.”

Peer Reviewed Surgical Mask to Prevent Influenza Transmission in Households: A Cluster Randomized Trial

“We evaluated the effectiveness of facemask use by index cases for limiting influenza transmission by large droplets produced during coughing in households. . . . In various sensitivity analyses, we did not identify any trend in the results suggesting effectiveness of facemasks.”

Peer Reviewed Is a Mask Necessary in the Operating Theatre?

“No masks were worn in one operating theatre for 6 months. There was no increase in the incidence of wound infection.”

“The finding that there was an appreciable fall in the wound infection rate when masks were not worn certainly warrants further investigation. This trial was designed only to see whether wound infection increased, as had been predicted, when masks were not worn. It did not. The conclusion is that the wearing of a mask has very little relevance to the wellbeing of patients undergoing routine general surgery and it is a standard practice that could be abandoned.”

Peer Reviewed Postoperative wound infections and surgical face masks: a controlled study

“It has never been shown that wearing surgical face masks decreases postoperative wound infections. On the contrary, a 50% decrease has been reported after omitting face masks. The present study was designed to reveal any 30% or greater difference in general surgery wound infection rates by using face masks or not. . . . [The results] indicated that the use of face masks might be reconsidered.”

Peer Reviewed An Experimental Study of the Efficacy of Gauze Face Masks

Completed by a scientist in the wake of the 1918 Spanish flu. He concludes that masks would need to be very thick to be effective and (even then) leakage out the side of the mask would be problematic.

“The reason for this apparent failure of the mask was a subject for speculation among epidemiologists, for it had long been the belief of many of us that droplet borne infections should be easily controlled in this manner. The failure of the mask was a source of disappointment, for the first experiment in San Francisco was watched with interest with the expectation that if it proved feasible to enforce the regulation the desired result would be achieved. The reverse proved true. The masks, contrary to expectation, were worn cheerfully and universally, and also, contrary to expectation of what should follow under such circumstances, no effect on the epidemic curve was to be seen. Something was plainly wrong with our hypotheses.”

“Masks have not been demonstrated to have a degree of efficiency that would warrant their compulsory application for the checking of epidemics.”

Peer Reviewed Analysis of the Effects of COVID-19 Mask Mandates on Hospital Resource Consumption and Mortality at the County Level

Bexar County is the 16th largest county in the United States, with a population of 2,009,324 as of April 1, 2020.

“[F]ew data are available to assess mask effects via executive order on a population basis. We assess the effects of a county-wide mask order... in Bexar County, Texas.”

“There was no reduction in per-population daily mortality, hospital bed, ICU bed, or ventilator occupancy of COVID-19-positive patients attributable to the implementation of a mask-wearing mandate.”

Peer Reviewed Contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers

“Respiratory pathogens on the outer surface of the used medical masks may result in self-contamination. The risk is higher with longer duration of mask use (>6h) and with higher rates of clinical contact.”

Low-cost measurement of face mask efficacy for filtering expelled droplets during speech

“We noticed that speaking through some masks (particularly the neck gaiter) seemed to disperse the largest droplets into a multitude of smaller droplets, which explains the apparent increase in droplet count relative to no mask in that case. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive.”

Aerosol filtering efficiency of respiratory face masks used during the COVID-19 pandemic

“Cloth masks were found to be ineffective for the assigned task.”

“Market available cloth masks were inefficient at any aerosol size range.”

Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review

“The evidence is not sufficiently strong to support widespread use of facemasks as a protective measure against COVID19. However, there is enough evidence to support the use of facemasks for short periods of time by particularly vulnerable individuals when in transient higher risk situations.”

Evidence for Community Cloth Face Masking to Limit the Spread of SARS‐​CoV‑2: A Critical Review

“More than a century after the 1918 influenza pandemic, examination of the efficacy of masks has produced a large volume of mostly low- to moderate-quality evidence that has largely failed to demonstrate their value in most settings.”

“The available clinical evidence of facemask efficacy is of low quality and the best available clinical evidence has mostly failed to show efficacy, with fourteen of sixteen identified randomized controlled trials comparing face masks to no mask controls failing to find statistically significant benefit in the intent‐​to‐​treat populations. Of sixteen quantitative meta‐​analyses, eight were equivocal or critical as to whether evidence supports a public recommendation of masks, and the remaining eight supported a public mask intervention on limited evidence primarily on the basis of the precautionary principle.”


Expert Commentary

A Virologist and WHO to Clarify: The Mouth-Nose Protection can be a breeding ground for many germs

Hendrik Streeck, professor for virology and the director of the Institute of virology and HIV Research at the University Bonn

“People crumple the masks in the pocket, touch you constantly, and strap yourself in for two weeks again and again in front of the mouth, probably unwashed.”

“This is a wonderful breeding ground for bacteria and fungi.”

Why is Sweden not recommending face masks to the public?

Johan Carlson, Director General of the Swedish Public Health Agency Folkhälsomyndigheten:

  • “Face masks in public spaces do not provide any greater protection to the population.”

Swedish state epidemiologist Anders Tegnell:

  • “The virus can gather in the mask and when you take it off, the virus can be transferred to your hands and thereby spread further.”
  • “Face masks can be effective against larger free floating particles, but nothing suggests that they help protect you from air-borne viruses.”

Are Face Masks Effective? The Evidence (Swiss Policy Research)

“So far, most studies found little to no evidence for the effectiveness of cloth face masks in the general population, neither as personal protective equipment nor as a source control.”

“In many states, coronavirus infections strongly increased after mask mandates had been introduced. . . . a direct comparison between US states with and without mask mandates indicates that mask mandates have made no difference.”

“The WHO admitted to the BBC that its June 2020 mask policy update was due not to new evidence but ‘political lobbying.’”

“There is still little to no scientific evidence for the effectiveness of cloth face masks in the general population, and the introduction of mandatory masks couldn’t contain or slow the epidemic in most countries. If used improperly, masks may increase the risk of infection.” (From summary of evidence on intro page, here:

Do face masks work? A note on the evidence

Former professor of pathology and NHS consultant: “These [cloth] masks are doing little.”

Is Routine Use of a Face Mask Necessary in the Operating Room?

“Recognizing the lack of sound scientific evidence, we have changed facemask routines in several units at the Karolinska University Hospital. . . . [T]he evidence to support this practice does not exist, and studies to establish differences in infection rates with or without face masks will likely be difficult to design and implement given the small potential effect.”

Standard Surgical Masks Do Not Protect Wearer From Getting Swine Flu

“Surgical masks will not block aerosolized particles as small as a droplet containing influenza virions from entering the airway. They essentially stop only spittle from a surgeon’s mouth and mucous from a surgeon’s nose from inadvertently dropping into a wound. . . . In addition to the too large pore size of a standard surgical mask, they are not form fitting to the face and allow “leakage” of aerosolized droplets around the edges.”

European Centre for Disease Prevention and Control. Using Face Masks in the Community: First Update.

Evidence for the effectiveness of non-medical face masks, face shields/visors and respirators in the community is scarce and of very low certainty. Additional high-quality studies are needed to assess the relevance of the use of medical face masks in the COVID-19 pandemic.” (Emphasis added.)

“Based on the assessment of the available scientific evidence, no recommendation can be made on the preferred use of medical or non-medical face masks in the community.”

“The very limited scientific evidence regarding the use of respirators in the community does not support their mandatory use in place of other types of face masks in the community.... [T]he difficulties to ensure their appropriate fitting and use in community settings as well as potential adverse effects related to lower breathability should be taken into account.”

World Health Organization

The WHO made headlines last summer when it changed its guidance on masks, but if you read the guidance released in June 2020, WHO still seems to have many reservations about the use of masks. And, as noted in the Swiss Policy Research link, the changed guidance was apparently prompted by political considerations, not scientific ones. Full disclosure: WHO watered down this guidance still more in December 2020, but left most of the list of potential harms.

“At the present time, the widespread use of masks by healthy people in the community setting is not yet supported by high quality or direct scientific evidence and there are potential benefits and harms to consider.”

“Potential harms/disadvantages

The likely disadvantages of the use of mask by healthy people in the general public include:

  • potential increased risk of self-contamination due to the manipulation of a face mask and subsequently touching eyes with contaminated hands;
  • potential self-contamination that can occur if non-medical masks are not changed when wet or soiled. This can create favourable conditions for microorganism to amplify;
  • potential headache and/or breathing difficulties, depending on type of mask used;
  • potential development of facial skin lesions, irritant dermatitis or worsening acne, when used frequently for long hours;
  • difficulty with communicating clearly;
  • potential discomfort;
  • a false sense of security, leading to potentially lower adherence to other critical preventive measures such as physical distancing and hand hygiene;
  • poor compliance with mask wearing, in particular by young children;
  • waste management issues; improper mask disposal leading to increased litter in public places, risk of contamination to street cleaners and environment hazard;
  • difficulty communicating for deaf persons who rely on lip reading;
  • disadvantages for or difficulty wearing them, especially for children, developmentally challenged persons, those with mental illness, elderly persons with cognitive impairment, those with asthma or chronic respiratory or breathing problems, those who have had facial trauma or recent oral maxillofacial surgery, and those living in hot and humid environments.


Mask Charts

These links look to correlation, none are controlled studies, but mask charts around the globe consistently show COVID cases increasing after mask mandates are implemented.  Do masks actively make things worse, as some of the studies above suggest they might?

Peer Reviewed Mask mandate and use efficacy for COVID-19 containment in US States

“We did not observe association between mask mandates or use and reduced COVID-19 spread in US states.”

Unmasked: Mask Charts from Ian Miller

“While we have no way to predict how far down the anti-science rabbit hole the CDC will continue to sink, we can look at how their guidance, their recommendation to wear masks is faring in a number of areas in the US and beyond that have followed their evidence-free advice.”

Effectiveness of mask mandates in jurisdictions worldwide to curb or reduce the spread of Covid-19.

For the latest charts illustrating the ineffectiveness of masks and mask mandates, Ian Miller on Twitter is an essential account to follow, and visit his account on Substack.

COVID-19 Mitigation Practices and COVID-19 Rates in Schools: Report on Data from Florida, New York and Massachusetts

“This paper reports on the correlation of mitigation practices with staff and student COVID-19 case rates in Florida, New York, and Massachusetts during the 2020-2021 school year. . . . We do not find any correlations with mask mandates.”

Mask mandate and use efficacy in state-level COVID-19 containment

“Case growth was independent of mandates at low and high rates of community spread, and mask use did not predict case growth during the Summer or Fall-Winter waves.”

“Conclusions: Mask mandates and use are not associated with slower state-level COVID-19 spread during COVID 19 growth surges. Containment requires future research and implementation of existing efficacious strategies.”

 

Negative Effects

Peer Reviewed Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?

This study documents negative physical, psychological, and developmental consequences from long-term mask use.  There are dozens of effects—too many to summarize here. The study is worth reading in full.

“Extended mask-wearing by the general population could lead to relevant effects and consequences in many medical fields. . . .  According to the scientific data, mask wearers as a whole show a striking frequency of typical, measurable, physiological changes associated with masks.”

Peer Reviewed Effect of a surgical mask on six minute walking distance

“Wearing a surgical mask modifies significantly and clinically dyspnea….”

Peer Reviewed Effect of facemasks on empathy and relational continuity: a randomised controlled trial in primary care

“In this large randomized controlled trial, we found that the wearing of facemasks by doctors had little effect on patient enablement and satisfaction but had a significant and negative effect on patients’ perceptions of the doctors’ empathy.”

“Facemasks offer limited protection in preventing infection and aerosol transmission through mucous membranes (i.e., conjunctivae). Meanwhile, a negative impact on the patient’s perceived empathy and relational continuity can reduce potential therapeutic effects such as decreased depression, improved immune response, improved quality of life and improved health outcomes.”

Peer Reviewed “Exercise with facemask; Are we handling a devil's sword?” - A physiological hypothesis

“Exercising with facemasks may reduce available Oxygen and increase air trapping preventing substantial carbon dioxide exchange. The hypercapnic hypoxia may potentially increase acidic environment, cardiac overload, anaerobic metabolism and renal overload, which may substantially aggravate the underlying pathology of established chronic diseases. Further contrary to the earlier thought, no evidence exists to claim the facemasks during exercise offer additional protection from the droplet transfer of the virus. Hence, we recommend social distancing is better than facemasks during exercise and optimal utilization rather than exploitation of facemasks during exercise.” 

Peer Reviewed Mask use during high impact exercise in the pandemic

“In case of intense physical exercise, the use of masks is not recommended because of the enhancing effect on PCO2. It would not allow the complete expulsion of the expired CO2 and would increase its concentration, along with the typical increase of the breathing rate during the exercise.”

Peer Reviewed Respiratory consequences of N95-type Mask usage in pregnant healthcare workers—a controlled clinical study

“Breathing through N95 mask materials have been shown to impede gaseous exchange and impose an additional workload on the metabolic system of pregnant healthcare workers.”

Peer Reviewed Headaches Associated With Personal Protective Equipment – A Cross-Sectional Study Among Frontline Healthcare Workers During COVID-19

“Most healthcare workers develop de novo PPE-associated headaches or exacerbation of their pre-existing headache disorders.”

“The magnitude of this condition is clinically significant and might worsen if the current outbreak spreads widely and stays for a longer time, affecting the work performance of healthcare workers.”

Peer Reviewed Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations

“Therefore, it can be concluded that N95 and surgical facemasks can induce significantly different temperatures and humidity in the microclimates of facemasks, which have profound influences on heart rate and thermal stress and subjective perception of discomfort.”

Peer Reviewed Use of face mask by blood donors during the COVID-19 pandemic: Impact on donor hemoglobin concentration: A bane or a boon

“This study including 19504 blood donors spanning over one and a half year shows that prolonged use of face mask by blood donors may lead to intermittent hypoxia and consequent increase in hemoglobin mass.”

Peer Reviewed A Study on the Effect of Wearing Masks on Stress Response

“It is well known that wearing a mask may cause breathing problems and hypoxia. And this situation will become more serious with the time of wearing the mask and the degree of protection of the mask. . . . Prolonged wearing may cause permanent damage to the respiratory system. Due to the lack of oxygen in the brain, it also damages our nervous system, causing adverse physiological reactions, such as dizziness, chest tightness, and psychological reactions about anxiety and depression. . . . We believe that as the duration of wearing a mask is longer, the more severe the situation of hypoxia, the more severe the body's response to hypoxia will be. The range of SDNN value decline will be greater. This also means that the people will suffer more stress, which harm people's health. Therefore, people need to know the negative effects of the mask and use the mask appropriately.”

Chemical cocktail found in face masks

“[M]ask wearers unwittingly run the risk of breathing in carcinogens, allergens and tiny synthetic microfibres by wearing both textile and nonwoven surgical masks for long periods of time.”

“'What we are breathing through our mouth and nose is actually hazardous waste,' said Professor [Michael] Braungart, [director at the Hamburg Environmental Institute,] who ran preliminary tests on used surgical masks that found traces of chemicals such as the known carcinogen aniline as well as formaldehyde and optical brighteners -- both heavily restricted on consumer goods by European and US authorities to minute parts per million concentrations.”

“[L]eading scientists are now questioning whether the real risk of exposure to potentially hazardous chemicals from long-term mask wearing is actually higher than the risk of coming into contact with the Sars-CoV-2 virus....”


Children and Masks

Peer Reviewed Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?

"Children are particularly vulnerable and may be more likely to receive inappropriate treatment or additional harm. It can be assumed that the potential adverse mask effects described for adults are all the more valid for children..... masks block the foundation of human communication and the exchange of emotions and not only hinder learning but deprive children of the positive effects of smiling, laughing and emotional mimicry. The effectiveness of masks in children as a viral protection is controversial, and there is a lack of evidence for their widespread use in children . . . . "

Peer Reviewed Masking Emotions: Face Masks Impair How We Read Emotions

“a mask obstructing a face limits the ability of people of all ages to infer emotions expressed by facial features, but the difficulties associated with the mask’s use are significantly pronounced in children aged between 3 and 5 years old. These findings are of essential importance, as they suggest that we live in a time that may potentially affect the development of social and emotion reasoning . . . .”

Association between School Mask Mandates and SARS-CoV-2 Student Infections: Evidence from a Natural Experiment of Neighboring K-12 Districts in North Dakota

“We observed no significant difference between student case rates while the districts had differing masking policies nor while they had the same mask policies. . . . Our findings contribute to a growing body of literature which suggests school-based mask mandates have limited to no impact on the case rates of COVID-19 among K-12 students.”

Study Summary at Brownstone Institute.

Impact of the COVID-19 Pandemic on Early Child Cognitive Development: Initial Findings in a Longitudinal Observational Study of Child Health

“We find that children born during the pandemic have significantly reduced verbal, motor, and overall cognitive performance compared to children born pre-pandemic. Moreover, we find that males and children in lower socioeconomic families have been most affected. Results highlight that even in the absence of direct SARS-CoV-2 infection and COVID-19 illness, the environmental changes associated COVID-19 pandemic is significantly and negatively affecting infant and child development.”

Dangerous pathogens found on children’s face masks

Parents in Florida sent their kids’ school masks to a lab for analysis. The masks had been worn for only one day.

The analysis detected the following 11 dangerous pathogens on the masks:

  • Streptococcus pneumoniae (pneumonia)
  • Mycobacterium tuberculosis (tuberculosis)
  • Neisseria meningitidis (meningitis, sepsis)
  • Acanthamoeba polyphaga (keratitis and granulomatous amebic encephalitis)
  • Acinetobacter baumanni (pneumonia, blood stream infections, meningitis, UTIs—resistant to antibiotics)
  • Escherichia coli (food poisoning)
  • Borrelia burgdorferi (causes Lyme disease)
  • Corynebacterium diphtheriae (diphtheria)
  • Legionella pneumophila (Legionnaires’ disease)
  • Staphylococcus pyogenes serotype M3 (severe infections—high morbidity rates)
  • Staphylococcus aureus (meningitis, sepsis)

Mandatory masks in school are a ‘major threat’ to children’s development, doctors warn

“Mandatory face masks in schools are a major threat to their development. It ignores the essential needs of the growing child. The well-being of children and young people is highly dependent on emotional attachment to others.”  

Doctors want coronavirus measures for under-12s in schools to be dropped

“‘Testing children, imposing mouth masks and quarantine go against the principle of “primum non nocere” (first, do no harm) which is included in the Hippocratic Oath that doctors took,’ the [Royal Academy of Medicine of Belgium] wrote in the statement. These drastic actions do much more damage to the children in the short and long term than going through the infection itself.”

The Londoner: Let children be exposed to viruses, says Professor Gupta

What if social distancing and over-sanitizing robs our kids of their opportunity to be low risk when it comes to COVID 19?

“[E]vidence is mounting that early exposure to these various coronaviruses is what enables people to survive them.”

The Science of Masking Kids at School Remains Uncertain

Over and over, studies and reports on children in schools with low transmission rates claim in their summaries that masking students helped keep transmission down. But looking at the underlying data in these studies, masks were always required or widely worn, and implemented in concert with a variety of other interventions, such as increased ventilation. Without a comparison group that didn't require student masking, it's difficult or impossible to isolate the effect of masks. (This is the error made by Duke University researchers who wrote a report about North Carolina schools, later summarized in a New York Times opinion piece.) I reviewed 17 different studies cited by the CDC in its K-12 guidance as evidence that masks on students are effective, and not one study looked at student mask use in isolation from other mitigation measures, or against a control. Some even demonstrated that no student masking correlated with low transmission.” [Emphasis added.]

COVID-19 School Response Dashboard

This website is worth exploring. It contains charts showing that “mask mandatory” schools did worse than “mask optional” schools last year. It also explores other social distancing measures.

School masks: face coverings could damage children's speech development, warn scientists

Newspaper reporting on the conclusions of the Children’s Task and Finish Group, endorsed by the Scientific Advisory Group of Emergencies (in the U.K.)

“detrimental development impacts [of masks] may be greater than the potential protective benefit”

“The risks of affecting or damaging general speech and language development is far greater than any risks of children transmitting.” 

“Viewing of faces is essential for brain development in both younger and older children, and in learning to speak/phonics, much of which is based on phonemic awareness.”


Making pre-school children wear masks is bad public health

Dr. Robert Hughes, who earned a Master in Public Health at the Harvard School of Public Health, is the lead author of this commentary.

“Children are not small adults. This is a critical point that many pediatricians and other child health professionals get bored of saying, yet it does seem to need repeating. While children have the lowest risk from COVID-19 directly, they risk suffering the indirect impacts of policy decisions, many of which appear to have been made with next to no explicit consideration of their interests. Public health interventions should not only be about infectious disease control, they should consider a broad set of outcomes. In addition, they ought to consider vulnerability, including that in early childhood -- a time when young children's brains are developing rapidly and are most susceptible to adversity. We believe that mandating masking of pre-school children is not in line with public health principles, and needs to be urgently re-considered.”

“the harms of this policy are likely to be damaging, potentially considerably so. Given this, and the influence that the CDC and Dr Fauci have both in the US and globally, we believe an urgent re-consideration of this policy is needed.”

The Case Against Masks for Children

Dr. Marty Makary, professor at Johns Hopkins School of Medicine, and Dr. H. Cody Meissner, chief of pediatric infectious diseases at Tufts Children's Hospital, make their case against masks for children.

“Those who have myopia can have difficulty seeing because the mask fogs their glasses.... Masks can cause severe acne and other skin problems. The discomfort of a mask distracts some children from learning. By increasing airway resistance during exhalation, masks can lead to increased levels of carbon dioxide in the blood. And masks can be vectors for pathogens.... Chronic and prolonged mouth breathing can alter facial development....”

“The possible psychological harm of widespread masking is an even greater worry.... Covering a child's face mutes these nonverbal forms of communication and can result in robotic and emotionless interactions, anxiety and depression.... The adverse developmental effects of requiring masks for a few weeks are probably minor. We can't say that with any confidence when the practice stretches on for months or years.”

The Science of Masking Kids at School Remains Uncertain

“Those who have myopia can have difficulty seeing because the mask fogs their glasses.... Masks can cause severe acne and other skin problems. The discomfort of a mask distracts some children from learning. By increasing airway resistance during exhalation, masks can lead to increased levels of carbon dioxide in the blood. And masks can be vectors for pathogens.... Chronic and prolonged mouth breathing can alter facial development....”


Suggest a Mask Study


Disclosures and Acknowledgments

MaskScience.org was created and is maintained by concerned volunteer citizens. We have no connection with and have received no funding or compensation from any third parties. We have no affiliation with any political or activist organizations, individuals, intermediaries, or proxies. We have no motive, ulterior or otherwise, other than aggregating and presenting authoritative, peer-reviewed information to help public and private sector decision-makers make evidence-based, data-driven choices.

Read why peer-review and randomized clinical trials (RCTs) are important tools to reduce bias, and understand why low quality observational studies are excluded from this site.

To help enhance and expand its accessibility, a substantial amount of content on this site has been duplicated from Mask Science with permission from its author. It has been supplemented with additional content. Where appropriate, the content has been updated to point to the latest revision of the study as it has worked its way through the peer-review process. The publishers of MaskScience.org thank all those who have contributed to this website for their hard work and effort.


But What About the Pro-Mask Studies?

Many pro-mask studies have emerged since April 2020. They are not included here for a few reasons:

(1) Why were these studies completed after the mask recommendation changed? Shouldn't science come first, changed recommendations second? Any pro-mask study completed after April 2020 must dot every “i” and cross every “t” to be included on this site.

(2) Most pro-mask studies do not do this. They rely on correlation, not causation. They study droplets in idealized lab conditions, often using mannequins instead of real people. They do not study transmission. They do not take into account real world usage, humidity, and other factors that will affect the cleanliness and quality of the masks. They do not look at the leakage that comes out the side of the masks.

As of this time, only one RCT exists that is supportive of masking (Abaluck, et al), informally known as the “Bangladesh study,” but it has yet to pass peer-review. Released as a pre-print on August 31, 2021, the Bangladesh study measured the impact of mask promotion on symptom reporting.

The Bangladesh study failed in several respects: The authors did not investigate what percentages of each population already had natural immunity to COVID-19. This fact, on its own, invalidates the whole study. But it gets worse. The authors also failed to isolate masks as the only variable that might lead to changed outcomes. (For instance, physical distancing also increased during the duration of the study, as the authors acknowledge. Did hand washing? The authors failed to document these variables.) The Bangladesh study has numerous additional limitations.

For an excellent analysis of the critical differences between the observational pro-mask studies and the RCTs casting doubt on the efficacy of masks, please read this article.


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Last Updated: July 21, 2022