Canada's chief public health officer and health minister say medical-grade masks need to be reserved for the use of front-line health workers — but it can't hurt for others to wear homemade masks or fabric face coverings, provided they do so properly.

"It's absolutely critical that if people are wearing masks outside — and it certainly is their prerogative to do that, by the way — that we are not taking away masks that are surgical or are specialized that are extremely necessary on the front line, and that we are not using masks in a way ... that is not appropriate," Health Minister Patty Hajdu said Wednesday.

Dr. Theresa Tam, chief public health officer of Canada, said the supply of medical-grade masks must be preserved for health system workers and those looking after patients infected with COVID-19.

"The effectiveness of the use of non-medical masks hasn't really been well demonstrated," said Tam. "But I think that there may not be any harm in wearing it, if one uses it properly — it's not gaping, it's really well fitted and you practice hygienic measures."

1/7 There is a lot of discussion on use of face masks. It can help to break the discussion into two main considerations regarding the TYPE of mask & the conditions for safe USE of masks in different circumstances/settings. <a href="https://twitter.com/hashtag/COVID19?src=hash&ref_src=twsrc%5Etfw">#COVID19</a> —@CPHO_Canada

Until recently, the federal government was saying that masks are unnecessary for those not exhibiting COVID-19 symptoms and that non-medical masks, or poorly-fitted medical masks, won't filter out the small airborne particles carrying the virus.

Health Minister Patty Hajdu and Canada's Chief Public Health Officer Dr. Theresa Tam say it's up to Canadians themselves to decide whether to wear homemade masks — but the science on their effectiveness is uncertain and the best protection against COVID-19 is still physical distancing. 4:28

But Tam said that the science on the use of masks and other medical responses to the novel coronavirus outbreak is changing.

"From a public health perspective, we need to take in evolution in information in science," she said. "We've been doing that, and these are the kinds of things that we discuss as a community of practices in terms of the public health and the chief medical officers."

Ontario Premier Doug Ford said he would continue to take his advice from health officials but that, in his opinion, wearing a mask could be safer than not wearing one.

"Are you safer with a mask? Absolutely, you're safer. I can't stand up here and say you would be safer without a mask, so my opinion, you'd be safer with a mask," he said Wednesday.

"But again, I'm going to stick with the advice of the chief medical officer of health and the medical professionals ..."

Masks have been used extensively in public in countries like China, Japan and South Korea, but the practice is not widespread outside of the region. That changed this week when Austria mandated that all people entering supermarkets or shops must wear masks. Other countries, such as Slovakia, the Czech Republic and Bosnia-Herzegovina, have implemented similar measures.

The argument against wearing masks in public were outlined by Hajdu and Tam on Wednesday. They insisted that masks that are not properly fitted will let contaminated particles pass. They also fear that masks could give people a false sense of security, leading them to let important hygiene measures slide.

Chief public health officer Dr. Theresa Tam speaks about how Canadians can safely use homemade masks or scarves, the evolution of thinking around masks and whether they actually help keep people safe. 1:59

"We also know what actually does work already, which is physical distancing," said Tam. "Those droplets fall a certain distance. That's why we've been recommending the two metre distance that actually works. Frequent hand washing absolutely works, not touching your face are absolutely proven measures and everyone should practise those regardless of what else you are adding to those layers of protection."

Tam and Hajdu also warned that masks have to be removed so that any contagious particles lodged in them don't find their way into someone's mouth or nose.

The upside to wearing masks

Tam said that there are clear positives to the use of non-medical, cloth or homemade masks.

"On the one hand, it might potentially reduce you from touching your nose or your mouth, if you've covered up those parts," she said. "But you have to be really careful then that you are not putting your finger in you eye when you're pulling your mask on and off, that you're [not] touching your face in other ways."

Masks are probably most useful, Tam said, as a way to catch the cough of someone wearing one, so that potentially infected droplets are not being spread around to other people or surfaces.

Tam said that people with COVID-19 who have been asked to isolate but need to go to essential appointments could wear masks to prevent themselves from spreading the virus. And anyone exhibiting symptoms, even mild ones, could wear a mask for the same reasons.