How does your body know where to form calluses on your hands or feet?

Friction: Body forms calluses at the sites of friction or excessive pressure.

Depends on the cause: Many things can cause calluses. Some reasons that one may develop a callus include: viral infections (warts), friction, pressure, repedetive trauma, and a limitation of joint motion. Some genetic conditions may also cause people to develop calluses on the hands and the feet. Treatment depends on the cause of the problem. Have it evaluated by a professional and get the appropriate treatment.