What condition is caused by repeated pressure on the skin, resulting in a protective layer?

A callus is formed as a protective response to repeated pressure or friction on the skin. This condition occurs when the skin thickens in order to protect underlying tissues from damage, often seen on hands or feet where there is frequent abrasion. The body naturally responds to persistent irritation by producing more skin cells, leading to the characteristic hardened area that provides additional cushioning and protection.

In contrast, a scar is the mark left after healing from an injury or wound, a blister is a fluid-filled sac resulting from friction or burns, and a wart is a benign growth caused by a viral infection. None of these conditions involve the same mechanism of protective thickening due to sustained pressure as seen in calluses. Understanding this distinction helps to recognize the different responses of the skin to varying types of stress and injury.