What triggers the formation of a callus on the skin?

The formation of a callus on the skin is primarily triggered by friction. When the skin undergoes repeated or excessive rubbing or pressure, it responds by thickening in that area as a protective mechanism. This thickened area is the body’s way of guarding against damage to the underlying tissues from continued friction. Calluses can often be found on hands and feet where such pressure is common, such as from gripping tools or walking.

While options involving infection, excessive moisture, and heat can affect skin health and lead to other conditions, they do not directly cause the skin to thicken and form a callus in the same way that friction does. Infections and excessive moisture could lead to different skin issues such as irritation or dermatitis, but the protective response of forming a callus is specific to mechanical stress like friction.