Fact check: False and misleading information in post listing ‘dangers’ of face masks

A Facebook post that lists dangers of wearing face masks contains false and misleading medical information.

Reuters Fact Check. REUTERS/Axel Schmidt

One example of the post (here) from has generated more than 2,000 reactions and 1,700 shares. It warns readers they should “know the facts” before wearing a face mask amid the COVID-19 pandemic, before detailing six alleged safety hazards.

These include claims of masks decreasing oxygen intake, increasing toxin inhalation, and shutting down the immune system. The post does not make a distinction between the different types of face mask available.

The first claim, which suggests that wearing a mask can reduce the amount of oxygen needed to stay healthy, is misleading. Writing for the American Lung Association (, pulmonologist David G. Hill, M.D answers the question “Do Masks Cause Low Oxygen Levels?” with the following: “Absolutely not. We wear masks all day long in the hospital. The masks are designed to be breathed through and there is no evidence that low oxygen levels occur. There is some evidence, however, that prolonged use of N-95 masks in patients with preexisting lung disease could cause some build-up of carbon dioxide levels in the body. People with preexisting lung problems should discuss mask wearing concerns with their health care providers.”

In an examination of the use of N-95 masks by healthcare workers, the U.S. Centers for Disease Control and Prevention (CDC) notes that a decrease in the frequency and depth of breathing may occur if the user experiences enough breathing resistance (here). However the CDC adds that this does not pose a significant risk when the N-95 mask is worn for periods of less than an hour.

Moreover, the close-fitting N-95 masks used by healthcare workers are different to cloth face coverings, which are the type advised by the CDC for use in public settings (here). The CDC’s guidelines on cloth face coverings are published here .

The second claim in the social media post, which suggests that wearing a mask can increase toxin inhalation due to exhaled waste being trapped, is also misleading.

Reuters has previously investigated claims of masks causing hypercapnia. This condition is caused by inhaling too much carbon dioxide, which is a waste gas released during exhalation.

A CDC spokesperson said on the topic: “The CO2 will slowly build up in the mask over time. However, the level of CO2 likely to build up in the mask is mostly tolerable to people exposed to it. You might get a headache but you most likely [would] not suffer the symptoms observed at much higher levels of CO2. The mask can become uncomfortable for a variety of reasons including a sensitivity to CO2 and the person will be motivated to remove the mask. It is unlikely that wearing a mask will cause hypercapnia” (here).

In the third claim, the post states that face masks put the body under stress, shutting down immune processes. In a previous fact check, Reuters could find no expert evidence to support the claim that wearing face masks weakens the immune system (here).

The fourth claim in the post incorrectly suggests that mask-wearing increases virus risk by “triggering and infection from dormant retro viruses already in the body”. The European Centre for Disease Prevention and Control told Reuters in a prior check that claims of “activating your own virus” within a mask were unsubstantiated (here).

According to the fifth claim, masks are “scientifically inaccurate” because the weaved material is too widely spaced to block coronavirus particles. While cloth masks may not prevent all respiratory droplets, which can carry the virus, from escaping, the CDC’s cloth face covering guidelines refer to “emerging evidence from clinical and laboratory studies that shows cloth face coverings reduce the spray of droplets when worn over the nose and mouth” (here).

The sixth and final claim in the post says there have been no peer-reviewed studies into the effectiveness of masks within a social environment. In June, the Lancet journal published the findings of an international research team that conducted a systematic review of 172 studies assessing distance measures, face masks and eye protection to prevent transmission of three diseases caused by coronaviruses - COVID-19, SARS and MERS (here ). The authors, did, however, say that further high quality research studies into the effectiveness of different types of mask was "urgently needed".


Mostly false. While more evidence is needed to give a complete picture of the effectiveness of public mask wearing in reducing viral transmission, it is not true to say that masks put people (who do not have breathing difficulties normally) at risk due to low oxygen levels, inhaled toxins, triggering of dormant viruses or the weakening of the immune system. N-95 masks as worn by medics may cause some physiological effects if worn for long periods without breaks.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here .