What causes blisters to form on the skin?

Blisters form primarily due to frictional forces acting on the skin. When sheer pressures are applied repetitively to an area of the skin, especially over a surface that is already somewhat sensitive or inflamed, it can lead to the separation of the skin layers. This separation forms a pocket between the epidermis and the dermis, which then fills with fluid. The fluid accumulation is a protective response from the body that cushions the underlying tissue, giving the blister its characteristic appearance.

While insect bites, allergic reactions, and heat exposure can also lead to skin changes and damage, they do not specifically cause blisters in the same mechanical way that friction does. Insect bites may result in swelling or hives, allergic reactions might lead to rashes or irritation, and heat exposure can cause burns or heat blisters, but the direct mechanism of blister formation through the separation of skin layers is most closely associated with frictional forces. Understanding this primary cause is crucial in fields like athletic training, where management and prevention of skin injuries is a significant concern for athletes.