Experts say you should make the request discreetly because shaming the person could put them on the defensive.

If they feel violated by the way you approach them, they are much less likely to make a change, said Jan Kavookjian, a behavioural scientist at Auburn University. She said citing local rules or recommendations from health officials could also help in some cases.

Rather than risk a confrontation, experts say it might be best to steer clear of people without masks in public if you can.

And if you’re in a store or restaurant, it’s best to have a manager or someone in charge ask the person, said Diane Gottsman, an etiquette expert.