A callus is a buildup of dead cells of skin or hyperkeratosis, in an area of ??skin. Such accumulation is a result of excessive friction, therefore, is a defense mechanism that triggers the skin. In the case of feet , this mechanism usually associated with abnormal patterns of motion or action of footwear. When the callus appears on the sole of the foot and is said to be caused by walking or footwear, which is incorrect. But when the callus appears between the toes, then we know that is caused by shoes that are ...