Small Toenail splitting/hardening
The small toenail is one that often becomes hard or splits. The usual reason for this is trauma from tight, narrow shoes. This type of shoe squeezes the toes, putting excessive pressure on the toenail. Direct trauma such as stubbing a toe also causes a split nail.
Some individuals have a curled fifth toe, meaning that their toe curls under the one next to it. In this case, the small toe has excessive pressure placed on it, causing the nail to become harder or split.