Ingrown nail
（重定向自Acronyx）
Onychocryptosis (from Greek ὄνυξ onyx "nail" + κρυπτός kryptos "hidden"), also known as an ingrown toenail, or unguis incarnatus 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. This condition has been found only in shoe-wearing cultures and does not occur in habitually barefoot people since it requires downward pressure on the nail by a shoe.