When you feel a sneeze or a cough coming on, covering your mouth prevents the spread of infectious germs. You probably knew that.

But the way you cover up also matters, and there are plenty of people who haven’t yet heard the consensus guidance of health officials: If no tissue is available, you should aim into your elbow, not your hand. Even if that means breaking a long-held habit.

“If somebody sneezes into their hands, that creates an opportunity for those germs to be passed on to other people, or contaminate other objects that people touch,” said Dr. Vincent Hill, chief of the waterborne disease prevention branch of the Centers for Disease Control and Prevention.

Germs are most commonly spread by the respiratory droplets emitted from sneezing and coughing. When they land on your hands, they’re transmitted to things like door knobs, elevator buttons and other surfaces the people around you are likely to also touch.