Plantar warts are small, rough growths on the feet. They usually show up on the ball/heel of the feet and the areas that bear the most pressure. This pressure may also cause a wart to develop a hard, thick layer of skin (callus).
Plantar warts are caused by HPV. This virus enters through tiny cuts or breaks on the bottom of the feet. While most plantar warts are not a major health concern, it is advised you see a doctor to have the warts examined and removed.