Callus

A callus (pl.: calluses) (also known as a tyloma) is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may occur anywhere on the skin. Some degree of callus, such as on the bottom of the foot, is normal.

Calluses are generally not harmful and help prevent blisters, as well as offering protection. However, excessive formation may sometimes lead to other problems, such as a skin ulceration or infection, or cause the affected person to try to offload the affected painful area, which can place excessive stress on the asymptomatic side.

Rubbing that is too frequent or forceful will cause blisters, as opposed to calluses, to form.

Cause

Normally, a callus will form on any part of the skin exposed to excess friction over a long period of time. Activities that are known for causing calluses include construction work and craftwork, the arts, food preparation, many sports and physical activities, and fashion choices like wearing high heels.

Although calluses can occur anywhere on the body as a reaction to moderate, constant "grinding" pressure, they are most often found on the foot (where the most pressure and friction are applied). On the feet (arguably the source of the most problematic calluses), they typically form on the metatarsal-phalangeal joint area ("balls of the foot"), heels and small toes due to the compression applied by tightly fitting shoes.