A callus is an abnormal thickening of the top layer of skin, which is composed of the natural protein, keratin. Calluses can form on areas that are repeatedly exposed to friction or pressure. They are usually painless or only mildly painful.

A corn is a small, well-defined, thickened area of skin that forms on the toes. Corns put pressure on the underlying skin against the bone. They are usually inflammed and painful.

A Corn
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Calluses and corns form as protective pads of skin in response to repeated friction or pressure. Causes include:

  • Calluses—Any activity that applies repeated friction or pressure to an area of skin, including:
    • Lifting weights (hands)
    • Using tools (hands)
    • Playing a stringed instrument (hands)
    • Running long distances (feet)
    • Kneeling to lay carpet or tile (knees)
    • Walking on hard surfaces without shoes (feet)
  • Corns—Any activity or condition that applies repeated friction or pressure to the toes, including:
    • Wearing ill-fitting shoes
    • Bunching of socks around toes
    • Socks with seams that rub against the toes
    • Foot abnormality causing a protrusion that rubs against footwear