There are several causes of blisters
are usually caused by injury to the skin
from heat or from friction, which create a tear between the epidermis—the upper layer of the skin—and the layers beneath.
Short periods of intense rubbing can cause a blister, but any rubbing of the skin at all can cause a blister if it is continued for long enough. Blisters form more easily on moist skin than on dry or soaked skin, and are more common in warm conditions.