Skin | Dermatology | Blisters (Symptom)
A blister is a collection of fluid beneath the outer layer of the skin that forms a raised area. They look like bubbles on the surface of the skin. A blister contains fluid that has leaked from blood vessels in underlying skin layers after minor damage and protects the damaged tissue. Small fluid-filled blisters are medically known as vesicles. Bullae are blisters that are larger than 1 cm across.
Most blisters are filled with a clear fluid called serum or plasma. However, blisters can be filled with blood, known as blood blisters or with pus, if they become infected. Depending upon the cause of the blisters, blisters may occur singly or in groups. In contrast to abscesses and boils, which are collections of inflammatory fluid found deep in the tissues, blisters are found in the most superficial layer of skin.
Common causes are burns and friction. Blisters may also occur with pemphigus, pemphigoid, dermatitis herpetiformis, some types of porhyria, and some skin diseases. These include eczema, epidermolysis bullosa, impetigo, and erythema multiforme. Small blisters develop in the viral infections chickenpox, herpes zoster (shingles), and herpes simplex.
Diagnosis and Treatment
Generally, blisters are best left intact, but large or unexplained blisters need medical attention.