The idea that beards are dirtier than clean-shaven faces has been floating around for decades, says John Tregoning, professor of vaccine immunology at Imperial College London. There is even research that shows people perceive bearded men as less hygienic: one study found restaurant customers rated waiters with facial hair as dirtier. Science doesn’t necessarily back that up, though.

One of the earliest studies on the subject, published in 1967, looked at how much bacteria could be recovered from men’s faces after being artificially sprayed on to their skin. Researchers compared washed and unwashed faces, both with and without beards. The dirtiest combination wasn’t with a beard: most bacteria was recovered from unwashed clean-shaven faces, followed by unwashed bearded faces, washed bearded faces and finally washed clean-shaven faces.

“So if you’re not going to wash your face, it’s better to have a beard,” says Tregoning, “but if you are going to wash your face, it’s slightly better to be clean-shaven.”

More recent research has focused on surgeons and healthcare workers, where the question is less about general hygiene and more about whether facial hair affects infection risk in operating theatres. Results have been mixed. Some studies suggest beards can trap bacteria, while others find little difference. Much depends on how samples are taken, and most studies suggest that if masks are worn properly there is no meaningful concern.

Overall, Tregoning says the idea that beards are unhygienic is overblown. “Everything has bacteria on it,” he says. “Any part of your body, with hair or without, is going to have bacteria on it. It’s not really a problem unless there’s an open wound. Most of the time it’s fine.”