A callus is caused by the buildup of hard, dead skin and can be found over an area of pressure or bony prominence. The hard skin is produced by special skin cells called keratinocytes, which are present throughout the entire epidermal layer of skin.
Calluses are the body’s attempt at protecting itself from friction or pressure, however, the extra skin can become painful and cause changes in how you walk. They are most common on the heel, the ball of foot, and the sides of the foot. Making sure you have sensible footwear is important.