ingrown nail

An ingrown nail, also known as onychocryptosis (from Ancient Greek: ὄνυξ, romanized: ónux, lit. 'nail'; and κρυπτός, kruptós, 'hidden') is a common form of nail disease. It is an often painful condition in which the nail grows so that it cuts into one or both sides of the paronychium or nail bed. While any nail can become ingrown, wearing shoes causes the toenails to grow in more often.

A common misconception is that the cause of an ingrown toenail is the nail growing into the paronychium, but it can also be caused by overgrown toe skin. The condition is caused by a microbial inflammation of the paronychium causing a granuloma within which the nail is buried. A true ingrown toenail is caused by actual penetration of flesh by a sliver of toenail.