Corns and calluses are your body’s response to friction or pressure against the skin. If your foot rubs the inside of your shoe, the affected area of skin thickens. Or, if a bone is not in the normal position, skin caught between bone and shoe or bone and ground builds up. In either case, the outer layer of skin thickens to protect the foot from unusual pressure. In many cases, corns and calluses look bad but are not harmful. However, more severe corns and calluses may become infected, destroy healthy tissue, or affect foot movement.
Corns usually grow on top of the foot, often at the toe joint. Corns can range from a slight thickening of skin to a painful soft or hard bump. They often form on top of buckled toe joints (hammer toes). If your toes curl under, corns may grow on the tips of the toes. You may also get a corn on the end of a toe if it rubs against your shoe. Corns can also grow between toes, often between the first and second toes.
Calluses grow on the bottom of the foot or on the outer edge of a toe or heel. A callus may spread across the ball of your foot. This type of callus is usually due to a problem with a metatarsal (the long bone at the base of a toe, near the ball of the foot). A pinch callus may grow along the outer edge of the heel or the big toe. Some calluses press up into the foot instead of spreading on the outside. A callus may form a central core or plug of tissue where pressure is greatest.