Blister

Blister, bubblelike, fluid-filled area on the skin that can be caused by friction, burns, contact with chemicals, or disease. A blister results from an accumulation of fluid beneath the outer layer of the skin (epidermis). The fluid is composed of sterile, clear serum or blood that has leaked from blood vessels into underlying tissue after injury. The fluid causes the epidermis to become inflamed, although the combination of the fluid and the inflammation protects deeper tissues from further injury.

Friction blisters commonly occur on the feet, where they usually result from flesh rubbing against shoe materials, and on the hands, where the strenuous use of tools may produce blisters on the fingers and palms. A second-degree burn is a burn severe enough to raise blisters on the skin, and bad cases of sunburn may also produce blistering. Blisters may be caused by frostbite, and they appear on the skin as a result of direct contact with such hazardous chemicals as mustard gas. Blisters are among the symptoms of such diseases as herpes, chicken pox, smallpox, and eczema, as well as fungus infections that may cause blisters on the feet.

Blisters should be covered with a bandage and left untouched until the body reabsorbs the collected fluid. If a blister does rupture, it will expose the sensitive underlying tissue to the air and to possible contamination from contact with infection-causing agents. A broken blister should be washed gently with mild soap and water, then covered with a sterile bandage. If a broken blister becomes progressively redder, and if red streaks beneath the skin appear to lead outwards from it, a physician should be consulted.