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

Melanonychia is a brown or black stain in your fingernail or toenail. You can have a dark line on one nail, a few nails, or all of your nails. The line is caused by the natural color in your body ...

When David Edges's wife spotted a faint brown line on his toenail, he didn't think it was anything to worry about. But Kelly, 47, a skin specialist in the beauty industry, was instantly concerned, ...

Experts review warning nail features, from inflammatory conditions to tumours, offering practical guidance on diagnosis and ...

If you're a runner, you know that black toenails are common—but that doesn't mean you have to put up with them. Beth Skwarecki is Lifehacker’s Senior Health Editor and has been writing about health, ...