Good Morning Britain 's Dr Sarah Jarvis has warned against removing your mask in a restaurant and then putting it back on when you leave.
She said you must put a clean one back on, and also warned not to pull it down over your chin and then back up over your mouth and nose.
This is because you can contaminate your mask with your hands, or even your chin and neck, then place it back over your mouth and infect yourself.
She was reacting to a baffling video from the US where restaurant diners were wearing two masks, one over each half of their mouth, opening their mouths to let in the food and completely defeating the point.
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