Blisters can form from continuous pressure or rubbing.
The outer membrane of a blister forms to protect the wound.
Continuous pressure or rubbing will eventually lead to the separation of the epidermis (the outer skin layer) from its lower skin layers, and a blister containing tissue fluid will form. This fluid is supposed to cushion the wound and protect it from further pressure. So actually, the blister is a clever self-protective measure created by your body.
„An open blister
The blister’s outer membrane is what successfully protects the wound from further pressure or from dirt or bacteria entering. Unfortunately, a blister is painful and can burst if exposed to more pressure and friction, leaving an open wound that is extremely painful and can easily become infected.