Why do people bite their nails?

Is nail biting actually that bad?

Here’s the thing: Some viruses live on surfaces and when we touch those spots (like doorknobs or subway rails) and then touch our eyes, nose, or mouths, we run the risk of helping those germs get into our bodies, Philip Tierno, Ph.D., microbiologist and clinical professor of pathology at NYU Langone, previously told SELF. It’s not a given that biting your nails will make you sick more frequently than those who don’t, but putting your fingers in your mouth isn’t doing your immune system any favors.