The World Health Organisation (WHO) says the widespread use of masks by the public will not stop the coronavirus pandemic.
The WHO recommends they be used in the community by people who are sick or their carers.
It also says they should be considered in countries that live in cramped conditions or have a lack of water to clean their hands.
But WHO director-general Tedros Ghebreyesus says they are not a 'silver bullet' to ending the virus.
"We know that medical masks can help to protect health workers but they are in short supply globally," WHO director-general Tedros Ghebreyesus said.
"We are concerned that the mass use of medical masks by the general population could exacerbate the shortage of these specialised masks for the people who need them most.
"This shortage is putting health workers in real danger."
Mr Ghebreyesus responded to scientists who had called on Africa to be a testing ground for a coronavirus vaccine describing them as racist.
Two French doctors called for Africa to be a testing ground for a vaccine because the people there are highly exposed.
"When we need solidarity, these kind of racist remarks do not help.
"Africa is not and will not be a testing ground for any vaccine.
"It was a disgrace and appalling to hear in the 21st century that kind of remark from scientists."
