A doctor tested her oxygen levels and heart rate while wearing face masks to show they don't make it hard to breathe

• Wearing a face mask helps prevent the spread of the novel coronavirus.
• But some people say they can't or won't wear one for a variety of medically invalid reasons, including they can't breathe or that oxygen levels drop behind a cloth shield.
• A doctor debunked these myths by testing her heart rate and oxygen levels while wearing different masks for five minutes each.
• Health professionals have also said claims that certain medical conditions should make you exempt from mask wearing aren't sound.

Face masks are recommended, if not required, in public settings throughout the US to protect wearers from contracting or spreading the novel coronavirus.

That's because they work. A recent study out of the UK, for example, showed that mandates to wear masks could be enough to contain an outbreak without a lockdown.

Case reports have illustrated their effectiveness too, with two infected (and masked) hairstylists able to do their jobs on 140 masked customers without spreading the illness.

But some Americans are pushing back, saying they're unable to breathe while wearing a mask or pointing to bunk science claims that the strips of fabric limit wearers' oxygen intake.

A doctor set out to prove them wrong. In an experiment she documented on Facebook, Megan Hall wore four different masks, each for five minutes, while testing her oxygen saturation and heart rate.

She found no significant change in either measure when she compared not wearing a mask with wearing various kinds of masks.

"Though maybe inconvenient for some, you can still breathe," she wrote. "As a physician, I urge you and ask you to please wear a mask to protect yourself and those who cannot safely wear a mask (many of my patients because they are under 2 years old)."

Other 'anti-maskers' have claimed they can't wear masks because of medical conditions, but doctors don't buy it

Other people have said they're "exempt" from mandates requiring mask wearing in public because they have a medical condition that makes the practice risky, according to Dr. Alan Hawxby, a transplant surgeon at the Oklahoma University Medical Center, who posted about the phenomenon on Twitter.

They say they're not required to disclose what that condition is because of privacy laws like HIPAA, which restricts the release of medical information.

Some falsely say that the Americans With Disabilities Act protects them from disclosing their "medical condition."

While it's true that wearing a mask can be uncomfortable, doctors say medical conditions don't excuse people from wearing masks — they emphasize the importance of wearing one correctly.

For people with asthma or chronic obstructive pulmonary disease, the arthritis organization CreakyJoints recommends staying home as much as possible and picking times when it's least hot, humid, and polluted to go out. It also says to choose a mask that's comfortable, like a cloth mask made with a moisture-wicking and breathable fabric, and practice wearing it.

The right mask fit is critical for healthcare workers too, for both safety and comfort, Christopher Friese, a professor of nursing at the University of Michigan who was on a National Academy of Medicine panel on respiratory protection, told Business Insider.

He said medical professionals and first responders should undergo a "fit test" to make sure they get an appropriate mask seal on their faces and be screened for conditions like asthma, allergies, and claustrophobia that could make wearing certain types problematic.

"In this pandemic, I fear that many settings are forgoing fit testing and that upfront screening for contraindications, which puts healthcare workers and first responders at risk," he said.