Blister

For other uses, see Blister (disambiguation).

Blister
Specialty	Dermatology

A blister is a small pocket of fluid within the upper layers of the skin. Blisters can be filled with blood (known as blood blisters) or with pus (if they become infected). However, most blisters are filled with a clear fluid called serum or plasma. Serum is the part of the blood that remains after red blood cells and clotting agents have been removed.

A blister usually forms because the outer layer of the skin has become damaged. Fluid collects under the damaged layer of skin, cushioning the tissue underneath, protecting it from further damage and allowing it to heal.

A blood-blister usually forms when a small blood vessel close to the surface of the skin ruptures (breaks) and blood leaks into a tear between the layers of skin. This can happen if the skin is crushed, pinched or squeezed very tightly.

Blisters can also form as the result of certain medical conditions.

Causes

Blisters are usually caused by injury to the skin from heat or from friction, which creates a tear between the epidermis—the upper layer of the skin—and the layers beneath. When this happens, the surface of the skin remains intact, but is pushed outwards as serum seeps into the newly created space between the layers.

Short periods of intense rubbing can cause a blister, as can any rubbing of the skin continued long enough. Blisters are most common on the hands and feet, as these extremities are susceptible while walking, running, or performing repetitive motions. Blisters form more easily on moist skin than on dry or soaked skin, and are more common in warm conditions.

Sometimes, the skin can blister when it comes into contact with a cosmetic, detergent, solvent or other chemical; this is known as contact dermatitis. Blisters can also develop as a result of an allergic reaction to an insect bite or sting.

There are also a number of medical conditions that cause blisters. The most common are chickenpox, herpes, impetigo, and a form of eczema called dyshidrosis. Other, much rarer conditions that cause blisters include:

• Bullous pemphigoid – a skin disease that causes large, tightly-filled blisters to develop, usually affecting people over the age of 60.
• Pemphigus – a serious skin disease in which blisters develop if pressure is applied to the skin; the blisters burst easily, leaving raw areas that can become infected.
• Dermatitis herpetiformis – a skin disease that causes intensely itchy blisters, usually on the elbows, knees, back and buttocks. The blisters usually develop in patches of the same shape and size on both sides of the body.
• Chronic bullous dermatosis – a disease that causes clusters of blisters on the face, mouth or genitals.
• Cutaneous radiation syndrome

Prevention

Blisters on the feet can be prevented by wearing comfortable, well-fitting shoes and clean socks. Blisters are more likely to develop on skin that is moist, so moisture-absorbing socks or frequent sock changes will aid those with particularly sweaty feet. While exercising or playing sports, special sports socks can help keep feet drier and reduce the chance of blisters.

Before going for a long walk, it is important to ensure that shoes have been broken in. If a hot area on the foot is felt, taping padding over the affected area can prevent the formation of a blister.

To avoid blisters on the hands, gloves should be worn when using tools such as a shovel or pickaxe, doing manual work such as gardening, and handling detergents, cleaning products, solvents and other chemicals.

A lubricant, typically talcum powder, can be used to reduce friction between skin and apparel. People put talcum powder inside gloves or shoes for this purpose.

Sunscreen and sun protection should also be used during the hottest part of the day to avoid blisters from sunburn, and moisturizing, after-sun or calamine lotions can help to ease discomfort in the case of burns.

Treatment

Most blisters heal naturally and do not require medical attention. As new skin grows beneath the blister, the fluid contained within it will be slowly reabsorbed by the body and the skin on top will dry and peel off.

The unbroken skin over a blister provides a natural barrier to infection, and patients should try to keep blisters intact and unbroken in order to avoid infection, ideally only allowing it to break on its own once the skin underneath has healed.

Blisters can sometimes become infected, typically with Staphylococcus aureus. This may be treated with antibiotics.

A common treatment used by medics in the U.S. Army is to drain the fluid from a blister and to inject the same amount of compound tincture of benzoin, to help seal the space created by the blister, to serve as a local antiseptic, and to prevent further abrasion or loss of skin.

See also

Buboe Dracunculiasis Herpangina

Herpes zoster Ulcer