Most of the time, thin, vertical black lines under your nails are no cause for concern. But if you've had them for a while or you just want to make sure they aren't a sign of something more serious, ...

The key to whether you should get any changes to your fingernails checked out is whether it appears on all your fingernails or just one. Usually longitudinal ridging appears on all fingers, but, says ...

Also, the cuticular seal of the nails should be intact, and the nail plate should adhere to the nail bed, says Dr. Thomas ...