Medically reviewed by Casey Gallagher, MD If your belly button smells, it's likely a sign of poor hygiene or an infection.

So for three years he collected his own belly-button lint to find out. And after interviewing ... but lint isn't the only thing inside these bizarre human crevices. Your belly button is a scar ...

“Also, if you develop a lump or swelling inside or around your belly button, it could be a hernia, which needs to be checked out by a doctor. Related: 6 Common Belly Button Infections to Know ...