A callus presents as a broad-based diffuse area of hard growth with relatively even thickness and it lacks a distinct border. The affected skin is rough and discoloured, varying in colour from white to grey-yellow or brown. They usually develop at the ball of the foot or around the heel area, but they can also be found on the palm of the hands or the knuckles.
Callus may also be spelled callous. A callus is sometimes referred to as callosity or tyloma in dermatology. A callus is a small area of thickened skin. The formation is caused by continued friction, pressure, or other physical or chemical irritation. Calluses form as result of a mild repetitive injury causing increased activity of the cell growth of the epidermis (the outermost layer of the skin). This gives the skin a local rise of increased tissue. Resulting in a hardened thickened pad of dead skin cells at the surface layer of the skin. Callus serves to protect underlying tissues.
Callus can form over any bony prominence. Calluses are most frequently seen on the hands and feet. The ball of the foot, the heel, and the underside of the big toe are commonly affected. However, they can occur anywhere. Callus can be annoying, but your body actually forms them to protect sensitive skin. Although calluses are typically benign, pressure or friction can precipitate pain. For foot calluses specifically, thin-soled and high-heeled shoes amplify discomfort. Relief comes with rest. Calluses are more common in women than men.
Calluses are often painless and can actually be advantageous to some athletes. Boxers and martial artists, for example, build up calluses on their hands to become more resistant to pain from impact. Dancers find that calluses can facilitate their performance of turns.