Onychocryptosis is the technical term for an ingrown toenail, this is an often painful condition in which the nail grows so that it cuts into one or both sides of the 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.
The common view is that the nail enters inside the paronychium but an ingrown toenail may be overgrown toe skin. The condition starts from a microbial inflammation of the nail bed, secondary to a over granulation, and the result is a nail buried inside the granuloma tissue. While ingrown nails can occur in the nails of both the hands and the feet, they occur most commonly with the toe. A true ingrowing toenail, or onychocryptosis, is caused by the actual penetration of the flesh by a sliver of nail.