Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing (friction), burning, freezing, chemical exposure, or infection. Most blisters are filled with a clear fluid called serum or plasma (aka, "blister water"). However, blisters can be filled with blood (known as blood blisters) or with pus (if they become infected).
The word "blister" entered English in the 14th century. It came from the Middle Dutch "bluyster", and was a modification of the Old French "blostre" which meant a leprous nodule -- a rise in the skin due to leprosy.
Causes
A blister may form when the skin has been damaged by friction or rubbing, heat, cold or chemical exposure. Fluid collects between the epidermis (the upper layer of the skin) and the layers below. This fluid cushions the tissue underneath, protecting it from further damage and allowing it to heal.
Continuous or repeated impact
Long-term spanking or whipping in the same spot, especially with implements with hard, sharp edges such as a paddle or cane that causes a pinching effect.
Friction or rubbing
Intense rubbing (or spanking) can cause a blister, as can any friction on the skin if continued long enough. This kind of blister is most common after walking long distances or wearing a poorly-tuned new pair of shoes. 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. Less aggressive rubbing over long periods of time may cause calluses to form rather than a blister. Both blisters and calluses can lead to more serious complications, such as foot ulceration and infection, particularly when sensation or circulation is impaired, as in the case of diabetes, neuropathy or peripheral artery disease (PAD).
Extreme temperature
The time of blistering is one of the tools used to determine the degree of burns sustained. First and second-degree burns may result in blistered skin; however, it is characteristic of second-degree burns to blister immediately, whereas first-degree burns can have blisters after a couple of days. Blisters can also form on the hands and feet as a result of tissue damage incurred by frostbite.
Chemical exposure
Sometimes, the skin will 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.
Crushing/Pinching
A blood blister usually forms when a minute 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 aggressively squeezed.
Disease
There are also a number of medical conditions that cause blisters. The most common are chickenpox, herpes (herpes simplex), 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
- Epidermolysis Bullosa
Prevention
Friction blisters
Friction blisters, caused by rubbing against the skin, can be prevented by reducing the friction to a level where blisters will not form. This can be accomplished in a variety of ways.
Blisters on the feet can be prevented by wearing comfortable, well-fitting shoes and clean socks. Inherently ill-fitting or stiffer shoes, such as high heels and dress shoes, present a larger risk of blistering. Blisters are more likely to develop on skin that is moist, so socks that manage moisture 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 also important to ensure that shoes or hiking boots have been properly broken in.
Even before a "hot" or irritated area on the foot is felt, taping a protective layer of padding or a friction-reducing interface between the affected area and the footwear can prevent the formation of a blister. Bandages, moleskin and tapes generally must be applied to the foot daily, and most have a very high coefficient of friction (COF), but a friction management patch applied to the shoe will remain in place much longer, throughout many changes of socks and insoles. This type of intervention may be used with footwear that is worn daily, with specialty shoes and boots like hockey skates, ice skates, inline skates, ski boots and cleats, or even with orthotic braces and splints.
To avoid friction blisters on the hands, gloves should be worn when using tools such as a shovel or pickaxe, doing manual work such as gardening, or using sports equipment like golf clubs or baseball bats. To further reduce the occurrence one can tape the hands, and there are also a number of products on the market that claim to reduce the occurrence of blisters. Many of these are found in off-road powersports. These are all intended to be worn as a liner underneath a glove. The majority of these offerings simply add padding and create a layer that reduces the coefficient of friction between the skin and the glove.
A lubricant, typically talcum powder, can be used to reduce friction between skin and apparel in the short term. People put talcum powder inside gloves or shoes for this purpose, although this type of lubricant will increase the friction in the long term, as it absorbs moisture. Increased friction makes blisters more likely.
Other
Sunscreen and sun protection should also be used during the hottest part of the day to avoid blisters from sunburn that can cause vamiclicitis. Protective gloves should be worn when handling detergents, cleaning products, solvents, and other chemicals.
Treatment
Friction blisters
Friction blisters are caused by excess shear stress between the surface of the skin and the body. The strata of skin around the Stratum lucidum is most susceptible to shear. As the Stratum lucidum tears away from the connecting tissues below, plasma from the cells diffuse out. This plasma solution helps new cells divide and grow into new connective tissues and epidermal layers.
The plasma solution will promote the growth of new cells and expedite proper healing and should not be drained. The clear fluid will be reabsorbed as new cells develop and the swollen appearance will subside. The time for blisters to heal depends on the location and the size of the area damaged. Protecting the blister from abrasion or additional shearing will help keep the blister intact.
Painful blisters located on hands (palmar surface) and feet (plantar surface) are due to tissue shearing deeper in the epidermis, near nerve endings. These especially should be kept intact if possible. Lower tissues are more susceptible to infection.
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.
Broken blisters can occasionally become infected. Infection should be prevented with antibiotics if possible and treated if necessary. There is heightened concern about MRSA and other kinds of infections from blisters, so they should be watched carefully.
Blisters due to sunburn
Most of these blisters will heal naturally. Moisturizing, after-sun or calamine lotions can help to ease discomfort in the case of burns.
See also Marks#Blisters and/or Blisters
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