8 Everyday habits that could shorten your lifespan

Nail biting

Think your nail-biting is just an annoying little tic? Think again. Nail biting can introduce both oral bacteria, such as eikenella corrodens, or skin bacteria, commonly streptococcus or staphylococcus, into the skin where they don't belong, explains Adam Friedman, MD, an associate professor of dermatology at George Washington School of Medicine and Hospital in Washington DC.