What triggers the formation of a callus on the skin?

The formation of a callus on the skin is primarily triggered by friction. When an area of the skin experiences repeated rubbing or pressure, the body responds by thickening the outer layer of skin, known as the stratum corneum. This process is a protective mechanism meant to prevent damage to the underlying tissues.

As friction continues, the skin builds up layers of dead skin cells, resulting in the hard, thickened area commonly known as a callus. Calluses are often found on areas of the body that endure consistent pressure, such as the soles of the feet or the palms of the hands. This natural response helps to shield the skin from injury and irritation.

While infection, excessive moisture, and heat can affect the skin in various ways, they do not specifically lead to the formation of calluses. For instance, infection can cause swelling or redness, excessive moisture might lead to maceration or softening of the skin, and heat can cause burns or irritation. None of these factors induce the same protective thickening response as friction does.