(See also Overview of Foot Problems.)
Corns and calluses are usually caused by intermittent friction and pressure, particularly in people who wear tight or ill-fitting shoes.
Corns caused by hammer toe and other toe deformities often develop on the tops of or at the tips of the toes, but corns most often develop on the tops of the toes over joints. These corns are hard. Corns that develop between the toes are soft. Corns may be pea-sized or slightly larger.
Calluses often develop on the ball of the foot because of faulty foot positioning and poor weight distribution. Calluses also develop on the sides of the feet in areas where pressure is increased.
Corns may be painful or tender when pressure is applied. A fluid-filled sac (bursa) sometimes forms beneath a corn.
Calluses usually do not cause symptoms. However, if friction is extreme, calluses may become thick and irritated, which causes a mild burning sensation, or sometimes a pain like that caused by damage to the nerves in the foot (interdigital nerve pain).
To remove thickened skin, people can use a nail file, emery board, or pumice stone immediately after bathing. People can apply keratolytics (agents that soften, loosen, and help the top layer of skin shed) to the affected areas.
To prevent corns and help treat existing corns, people can use cushioning and devices that redistribute pressure from the affected areas. Padding of various sorts (for example, felt or moleskin or foam-rubber protective bandages) and devices placed in the shoe (orthoses) or other inserts that have padding and support can help reduce pressure. Dells, which are holes cut through part of the footwear beneath the area that is painful, can also help reduce pressure and pain.
Regular care from a podiatrist (a doctor specializing in foot care) is helpful for people who have a tendency to develop calluses and corns. Proper foot care is important (see Caring for the Feet).
People who have disorders that impair normal nerve function (neuropathy) and circulation of blood, such as diabetes, are at increased risk of developing open sores (ulcers) in their feet when the skin is damaged (see sidebar The Foot in Diabetes). These ulcers can become infected. Doctors may choose not to surgically treat corns and calluses in people who have these underlying disorders. In these cases, special shoes and shoe inserts that reduce pressure over the affected area may be necessary and beneficial.
People should be taught how to inspect their feet for ulcers at home and how to prevent ulcers.