Blister

A blister is a bubble of fluid under the skin. The clear, watery liquid inside a blister is called serum. It leaks in from neighboring tissues as a reaction to injured skin. If the blister remains unopened, serum can provide natural protection for the skin beneath it. Small blisters are called vesicles. Those larger than half an inch are called bullae. A blood blister is filled with blood, rather than serum.

There are many causes of blisters, including:

Irritation — Blisters can be caused by physical factors that irritate the skin, such as friction (rubbing the skin), irritating chemicals or extreme cold or heat. Blisters on the feet can result from shoes that are either too tight or rub the skin in one particular area. Blisters also can be caused by contact dermatitis, a skin reaction to some type of chemical irritant. Intense cold can trigger frostbite, which often leads to blisters once the skin is rewarmed. Any type of burn, even sunburn, also can cause blisters.

Allergies — Allergic contact dermatitis, a form of dermatitis or eczema, may result in blisters. Allergic contact dermatitis is caused by an allergy to a chemical or poison, such as poison ivy, poison oak or poison sumac.

Infections — Infections that cause blisters include bullous impetigo, an infection of the skin caused by staphylococci (staph) bacteria; viral infections of the lips and genital area due to the herpes simplex virus (types 1 and 2); chickenpox and shingles, which are caused by the varicella zoster virus; and coxsackievirus infections, which are more common in childhood.

Skin diseases — Numerous skin diseases cause blisters. Examples include dermatitis herpetiformis, pemphigoid and pemphigus. There also are inherited forms of blistering skin conditions, such as epidermolysis bullosa (in which pressure or trauma commonly leads to blisters) and porphyria cutanea tarda (in which sun exposure provokes blisters).

Medications — Many medications, such as nalidixic acid (NegGram) and furosemide (Lasix), can cause mild, blistering skin reactions. Others, such as the doxycycline (Vibramycin), can increase the risk of blistering sunburn by increasing the skin's sensitivity to sunlight. In more dramatic cases, medications can trigger more severe, even life-threatening, blistering disorders, such as erythema multiforme or toxic epidermal necrolysis, also known as TEN, an illness that causes severe skin damage and typically involves 30% or more of the body's surface.

Irritation — Blisters can be caused by physical factors that irritate the skin, such as friction (rubbing the skin), irritating chemicals or extreme cold or heat. Blisters on the feet can result from shoes that are either too tight or rub the skin in one particular area. Blisters also can be caused by contact dermatitis, a skin reaction to some type of chemical irritant. Intense cold can trigger frostbite, which often leads to blisters once the skin is rewarmed. Any type of burn, even sunburn, also can cause blisters.

Allergies — Allergic contact dermatitis, a form of dermatitis or eczema, may result in blisters. Allergic contact dermatitis is caused by an allergy to a chemical or poison, such as poison ivy, poison oak or poison sumac.

Infections — Infections that cause blisters include bullous impetigo, an infection of the skin caused by staphylococci (staph) bacteria; viral infections of the lips and genital area due to the herpes simplex virus (types 1 and 2); chickenpox and shingles, which are caused by the varicella zoster virus; and coxsackievirus infections, which are more common in childhood.

Skin diseases — Numerous skin diseases cause blisters. Examples include dermatitis herpetiformis, pemphigoid and pemphigus. There also are inherited forms of blistering skin conditions, such as epidermolysis bullosa (in which pressure or trauma commonly leads to blisters) and porphyria cutanea tarda (in which sun exposure provokes blisters).

Medications — Many medications, such as nalidixic acid (NegGram) and furosemide (Lasix), can cause mild, blistering skin reactions. Others, such as the doxycycline (Vibramycin), can increase the risk of blistering sunburn by increasing the skin's sensitivity to sunlight. In more dramatic cases, medications can trigger more severe, even life-threatening, blistering disorders, such as erythema multiforme or toxic epidermal necrolysis, also known as TEN, an illness that causes severe skin damage and typically involves 30% or more of the body's surface.

There are many activities and ailments that can induce blistering. Below are some of the more common ways that blisters can form.

Friction

Blisters are most commonly formed due to excess friction, often caused by repetitive actions such as playing a musical instrument.

Any repetitive friction or rubbing can cause blisters.

These blisters will usually appear on the hands or feet, as these are the areas that most often encounter repetitive abrasion, whether walking, running or playing the drums.

Areas of skin with a thick horny layer, attached tightly to underlying structures (such as palms of hands and soles of feet) are more likely to generate blisters.

Blisters occur more readily if the conditions are warm, for example, inside a shoe. They also form more easily in damp conditions, compared with wet or dry environments.

Blisters can lead to more serious medical issues such as ulceration and infection, although, under normal conditions, this is rare.

Temperature extremes

The timing of blister formation helps categorize burns. Second-degree burns will blister immediately, but first-degree burns blister a couple of days after the incident.

At the opposite end of the spectrum, frostbite also produces blisters. In both cases, the blister is a defense mechanism deployed to protect lower levels of skin from temperature-related damage.

Chemical exposure

Skin can occasionally blister because of certain chemicals. This is known as contact dermatitis.

It can affect some individuals on contact with the following:

cosmetics

detergents

solvents

nickel sulfate, used in electroplating

balsam of Peru, a flavoring

insect bites and stings

chemical warfare agents, including mustard gas

Crushing and pinching

If a small blood vessel near the surface of the skin is ruptured, blood can leak into the gap between the layers of skin causing a blood blister to form. This is a blister filled with blood.

Medical conditions

A number of medical conditions can cause blisters.

These include:

Chickenpox: The rash forms small blisters that eventually scab over.

Herpes: The cold sores produced by the herpes simplex virus are clusters of blisters.

Bullous impetigo: Mostly seen in children under 2 years, blisters can form on the arms, legs, or trunk.

Eczema: Blistering can occur alongside a number of other skin symptoms such as cracking, crusting, and flaking.

Dyshidrosis: A skin condition characterized by a rapid occurrence of many small, clear blisters.

Bullous pemphigoid: An autoimmune disease that affects the skin and causes blisters, this is most common in older patients.

Pemphigus: A rare group of autoimmune diseases, this affects the skin and mucous membranes. The immune system attacks an important adhesive molecule in the skin, detaching the epidermis from the rest of the layers of skin

Dermatitis herpetiformis: This chronic blistering skin condition is unrelated to herpes but similar in appearance.

Cutaneous radiation syndrome: These are the effects of exposure to radiation.

Epidermolysis bullosa: This is a genetic disease of the connective tissue that causes blistering of the skin and mucous membranes.

Some studies found women to be more susceptible: Patterson et al²² found women were 1.6 times more likely to blister. Brennan et al²⁶ found women were more likely: 47% vs 30%. And finally, Veijgen et al²⁷ found that women were more likely to have a higher skin coefficient of friction compared to men.Wearing ill-fitting shoes.

Repetitive work with hand tools.

Getting a sunburn or frostbite.

Severe skin swelling, especially of the legs.

An infected blister will be filled with yellow or green pus and may be painful, red and hot. It's important not to ignore an infected blister because it could lead to secondary impetigo (a contagious bacterial infection of the skin) and further complications, such as cellulitis or sepsis.

You have several options for preventing blisters. Most involve preparation and caution. Preventing blisters depends on the type of blister:

Friction blisters: Friction blisters result from repeated rubbing. To prevent them:

Make sure your shoes fit well and do not rub.

Break in new shoes before wearing them for extended periods.

Wear gloves to protect your hands if you plan on doing a lot of manual labor.

Wear properly fitting clothes to prevent chafing that can lead to blisters on other parts of your body.

Blood blisters: These blisters usually develop when something pinches part of your skin. They typically happen on the hands. It’s harder to prevent them, but take these steps:

Stay alert when using tools or things that can pinch.

Wear gloves when working with pruners, strong pliers or in other tight situations.

Heat blisters: Heat blisters can result from a burn or when your skin gets too hot as you recover from frostbite. To prevent them:

Use sunscreen if you plan to be in the sun for an extended period.

Be extra careful when handling hot items or working around a fire.

Wear weather-appropriate clothing to avoid frostbite. If your skin gets frostbitten, slowly raise your body temperature using lukewarm water.

Protect your feet. To prevent blisters on your feet, wear nylon or moisture-wicking socks. ...

Wear the right clothing. ...

Consider soft bandages. ...

Apply powder or petroleum jelly to problem areas. ...

Stop your activity immediately if you experience pain or discomfort, or if your skin turns red.