You’ve probably seen the calls for DIY fabric face masks for hospitals and care facilities in recent weeks, and if you have a sewing machine perhaps you’ve made some yourself. Now there are suggestions that maybe all of us should be wearing masks. If we do, homemade fabric masks could be a responsible choice that preserves medical-grade masks for medical professionals.
But do they work? And is the habit of wearing them likely to do more harm than good? The answer is: it’s complicated. But if you decide you’d like to make masks for yourself or others, here’s what you need to know.
Fabric masks don’t work as well as surgical masks
There are two studies that I’ve seen repeatedly cited to show that fabric masks may be effective for the general population, and one in health care workers that seems to show the opposite. Let’s take a look at them.
Before we start talking about how effective fabric masks are, it’s important to consider how they’re being used, so we can say: effective for what? There are three main use cases people are discussing, so let’s disentangle these threads so we can look at each:
healthcare workers, as a replacement for medical masks or in addition
sick people, to avoid transmitting germs to others
healthy people in everyday life, to reduce their risk of contracting infection
People who believe they are healthy may turn out to unknowingly be sick, so when we talk about mask-wearing by the general public, this is often a mix of protecting the wearer from others and protecting others from the wearer.
None of these three studies accurately capture all of the effects of telling a population to wear (or not wear) masks. They each only look at a specific scenario and study it in one narrow way.
One study, published in PLoS One in 2008, measured the number of particles on either side of a mask worn by a study volunteer as they sat, spoke, and walked. In the study, n95 masks filtered particles (including respiratory droplets) better than surgical masks, which in turn worked better than mask made out of a tea towel.
The authors concluded that homemade masks are imperfect but could provide some protection if worn by the general public. But it’s important to remember that volunteers were only asked to wear the masks for a few hours in a specific laboratory experiment, doing things that the researchers asked them to do.
The investigators did consider the question of whether people would take off their mask when they weren’t supposed to, and found that compliance was better with the homemade masks, suggesting they may be more comfortable. But they didn’t look specifically at people’s ability and willingness to observe mask hygiene, which includes knowing when and how to change masks.
Another study, published in Disaster Medicine and Public Health Preparedness in 2013, asked volunteers to make their own masks. Then they tested whether those masks block bacteria when the (healthy) volunteers coughed, and they used a machine to test the filtration capability of different materials, including cotton t-shirt fabric and pillowcases.
This study is often cited as showing that fabric masks “work,” but when you get into the details, there are plenty of caveats. The masks were tested when fresh and dry, with the investigators noting that after a mask gets damp from use, the results don’t apply. Homemade masks didn’t filter as well as surgical masks, and they didn’t fit as well, either.
The researchers conclude: “An improvised face mask should be viewed as the last possible alternative if a supply of commercial face masks is not available...However, these masks would provide the wearers little protection from microorganisms from other persons who are infected with respiratory diseases. As a result, we would not recommend the use of homemade face masks as a method of reducing transmission of infection from aerosols.”
A third study, published in BMJ Open in 2015, was a randomised trial looking at whether healthcare workers who wore cloth masks throughout their shift were more likely to get sick than those who wore medical masks for the whole shift, or who used masks occasionally. (Nobody in the study went entirely without masks.)
This study found that hospital staff who wore cloth masks for their whole shift were more likely to get sick than the other two groups. It’s possible that wearing cloth masks increased their risk, but since there was no group that went maskless, it’s not possible to say that cloth masks are worse than nothing—only that the ones in this study are worse than using surgical masks either continuously or occasionally.
We still don’t have a study that looks at whether making a habit of mask wearing is likely to protect people in the general population as we go about our day. Based on these studies it’s possible, but not definitively known, that a properly worn mask is better than nothing.
There’s still not a clear-cut answer about whether the general public should wear masks
Lately, there have been several impassioned pleas to get people to wear masks when they go out in public. Some news outlets have been reporting that the CDC is considering changing their guidance to begin recommending them. The CDC tweeted on March 28 that they have no guidance changes “scheduled,” which I suppose could mean that they’re thinking about it. Dr. Fauci told CNN that the idea of recommending masks to the public is “under very active discussion,” with the main concern being to make sure that any such recommendation doesn’t worsen the shortage of personal protective equipment (PPE) for medical professionals.
Zeynep Tufekci has argued that telling people not to wear masks was a confusing message. Masks are desperately needed by healthcare professionals, so we must conserve them; but if they work so well, why shouldn’t the rest of us wear them too?
These facts aren’t actually in conflict, but it can seem that way. As we wrote back in February, getting masks to healthcare professionals is top priority. If the supply of masks were endless, it might make sense to say that everyone can choose for themselves whether they’d like to wear a mask.
But the supply is limited, and that’s been the case since the very beginning of the outbreak in Wuhan. (Science journalist Maryn McKenna warned us in 2018 that, since most of our masks are made in China and Mexico, that a pandemic that starts in either of those countries could dry up the supply of masks before that pandemic reaches us. And that’s exactly what happened.)
When there is a shortage of masks, it’s most important for healthcare workers to have them. The rest of us can do without. That’s why the World Health Organisation has been saying throughout this pandemic that you only need a mask if you are sick or if you are taking care of someone who is. “If you are not ill or looking after someone who is ill then you are wasting a mask,” they say on their Q&A page. But they’re talking about medical-grade masks, and say nothing about the cloth kind.
Mask hygiene is important
Protecting yourself with a mask is not as simple as just putting one on. Even if masks work, everything else you do affects your chances of contracting or spreading illness as well.
For example, if you feel safer wearing a mask, you could put yourself more at risk by going shopping more often, or getting closer to people.
If you touch your mask and then touch your face or touch any nearby surfaces, you could be contaminating your face or those surfaces.
When you take off the mask, you could get infectious particles on your hands. And if somebody else handles the mask—while doing laundry, for example—they could be exposed as well.
The World Health Organisation’s advice on mask usage assumes disposable masks, such as when they tell you to immediately discard masks after use in a trash can with a lid. Still, if you’re going to wear a mask, you should know how to use it. WHO advises:
Before putting on a mask, clean hands with alcohol-based hand rub or soap and water.
Cover mouth and nose with mask and make sure there are no gaps between your face and the mask.
Avoid touching the mask while using it; if you do, clean your hands with alcohol-based hand rub or soap and water.
Replace the mask with a new one as soon as it is damp and do not re-use single-use masks.
To remove the mask: remove it from behind (do not touch the front of mask); discard immediately in a closed bin; clean hands with alcohol-based hand rub or soap and water.
Fabric masks are not a replacement for medical-grade masks for healthcare workers
So what about the masks that volunteers are sewing for hospitals and care facilities? Cloth masks are problematic there, as you may recall from the study that found hospital workers were more likely to get sick if they wore cloth masks throughout their shift than if they used medical grade masks. While there are plenty of institutions requesting masks, I’ve also corresponded with several nurses who are appalled that any medical facilities are even considering it.
So let’s make one thing clear: fabric masks are not considered PPE. They do not substitute for the actual N95 or surgical masks that hospital staff wear. You may have heard that the Centres for Disease Control recommends them as a “last resort,” but they’re, like, really last. Here’s what the CDC says:
In settings where face masks are not available, [healthcare providers] might use homemade masks (e.g., bandana, scarf) for care of patients with COVID-19 as a last resort. However, homemade masks are not considered PPE, since their capability to protect [healthcare providers] is unknown. Caution should be exercised when considering this option. Homemade masks should ideally be used in combination with a face shield that covers the entire front (that extends to the chin or below) and sides of the face.
This recommendation comes at the very, very, very bottom of the CDC’s strategies for optimising the supply of face masks. Strategies that are more highly recommended include:
looking for additional medical-grade masks (asking for donations, buying from places other than the usual suppliers)
limiting the number of patients that come into clinics at all and cancelling elective procedures and appointments
reducing the number of times a provider would have to put on a mask (for example, setting limits on the number of people in a patient room or operating room)
using masks after their expiration date
The recommendations also include, if necessary, restricting the available masks to providers only. Normally patients who are infectious may be asked to wear a mask as “source control.”
If you keep scrolling down the page, you find a grim section about what to do if there are no face masks available at all. One suggestion is that COVID-19 patients could be cared for by providers who have themselves had and recovered from COVID-19. Another is is to use clear plastic face shields without a mask. Finally, at the end, is the suggestion to use homemade masks, and if doing so to cover them with a face shield.
In other words, homemade masks for medical professionals are considered to be maybe better than nothing at all. They are no replacement for respirators, or splashproof surgical masks, or even medical grade procedure masks. But if things get dire enough, they may be used.
Who is using donated masks?
Before contributing to a crafting project, it’s important to find out where your finished objects will be going, and whether they’re needed. Charity crafting projects often spiral out of control, like the call for penguin sweaters that was quickly answered. Tiny sweaters kept pouring in, so penguin rescuers started putting them on stuffed penguins to sell as a fundraiser. Or perhaps you’ll remember the koala mitten debacle, where an organisation called for mittens for koalas’ burned paws but soon was asking people to please, please not send mittens after all.
The shortage of PPE is real, and of potentially life-or-death concern. If you make masks, you are not making PPE. But some clinics and care facilities are accepting homemade masks, either as potential worst-case-scenario protection as we discussed above, or for purposes including:
Reducing the chance of sick patients or residents transmitting the virus to others (in this case the fabric mask goes on the patient, not the provider)
Attempting to prolong the useful life of PPE such as N95 masks. In many hospitals, staff are issued one N95 mask per day and are expected to reuse it. This is not normally recommended, but some staff say the fabric masks can help them keep their mask from getting visibly soiled, which would require them to discard it.
These are dark times if hospital workers can’t get the PPE they need—but supplies are already low, and everybody is doing what they can. Masks for the general public may be one solution to help slow the transmission of the coronavirus, but they have plenty of caveats and unknowns.