Callouses and corns are areas of skin that thicken, after exposure to repetitive forces, in order to protect the skin. When a callous develops a mass of dead cells in its center, it becomes corn. Corns generally occur on the toes and balls of the feet. They are generally symptoms of underlying problems and in some instances, an early warning sign of more complex foot problems. A callous or corn will require treatment when they become painful. If you suffer from diabetes, poor blood circulation, or loss of sensation (neuropathy), you should seek professional treatment even if there is no associated pain.