Blisters

Blisters

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.

Friction or Rubbing

Intense rubbing 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, 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

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