What is a blister that contains water called?

A blister that contains water is called a bulla. In dermatological terms, a bulla is defined as a large fluid-filled sac on the skin that typically contains clear fluid. It is larger than a vesicle, which is a smaller blister. The presence of water, or clear fluid, in a bulla distinguishes it from other skin lesions that may be solid or filled with pus, like papules. Additionally, a macule is simply a flat, discolored spot on the skin without elevation or fluid, making it unrelated to blisters. Understanding these terms is essential in both skin health and the practice of cosmetology, where recognizing different skin conditions can inform treatment and care.