A black line on your nail (medically known as melanonychia) causes a streak of dark pigmentation that runs along the nail bed ...

"Bleeding under the nail can sometimes look very black," she said. "Usually this is in the toenails, especially the large one. "However, a new dark line in a light-skinned person’s nail, especially ...

Have you ever taken off your nail polish only to notice a dark line on the nail running vertically down your finger? These ...