A black line on your nail (medically known as melanonychia) causes a streak of dark pigmentation that runs along the nail bed. It can be a normal color variation, especially in people with darker ...

Michelle Tagliamonte, 58, was getting a manicure when she noticed the black lines on her thumb, which signaled the start of a ...

A black line on the nail could be normal, such as when it is just a color variation. Other possible causes range from injury to certain medications for conditions like human immunodeficiency virus ...