A corn or callus is a thickened area of skin on the foot caused by an abnormal position of the underlying bone from repeated rubbing and pressure. The rubbing causes the skin to produce a layer of protective skin (a corn or callus). Corns occur on the top of the foot and calluses occur on the bottom of the foot. They can vary in size, and become painful. Treatment for painful corns and calluses involves trimming or debriding the thickened skin, however this does not cure the problem. Corns and calluses return after they are trimmed due to the bony prominence underneath them. Orthotics may help to alleviate pressure on the bony prominences. Surgical correction of the underlying cause may be indicated to resolve the problem.