A blister is a pocket of fluid between the upper layers of skin. The most common causes are friction, freezing, burning, infection, and chemical burns. Blisters are also a symptom of some diseases.
The blister bubble is formed from the epidermis, the uppermost layer of skin. Its purpose is to protect and cushion the layers below. Blisters can be filled with serum, plasma, blood or pus depending on how and where they are formed.
This stops further damage and gives the tissue time to heal.
In this article, we will discuss what blisters are, how they are caused and the best ways to prevent and treat them.
Fast facts on blisters
- Blisters are filled with serum, plasma, blood, or pus.
- Friction, burns, frostbite, and some medical conditions can produce blisters.
- Blisters help prevent further damage to deeper tissues.
- It is best to leave blisters intact to protect the underlying layers from infection.
- Wear well-fitting shoes and avoiding exposure to certain chemicals can prevent blisters from occurring.
There are many activities and ailments that can induce blistering. Below are some of the more common ways that blisters can form.
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.
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.
Skin can occasionally blister because of certain chemicals. This is known as contact dermatitis.
It can affect some individuals on contact with the following:
- 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.
A number of medical conditions can cause blisters.
- 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.
The main types of blisters are:
- friction blisters
- blood blisters
- heat blisters
Other types of blister are named after the condition they are linked to, such as chickenpox and shingles blisters and atopic eczema blisters.
Bunions: What you need to know
Bunions are another problem that can affect the feet
How they form
The most common type of blister for most individuals is the friction blister. In their most basic form, they occur due to increased shear stress between the surface of the skin and the rest of the body.
The layer of the skin most susceptible to shear forces is the stratum spinosum. As this layer tears away from the tissues below, a plasma-like fluid leaks from the cells and begins to fill the gap that is created. This fluid encourages new growth and regeneration.
Roughly 6 hours after the blister appears, cells at the base of the blister start to take up amino acids and nucleosides. These are the building blocks of protein and DNA.
At 24 hours, cell division is markedly increased. New skin layers above the stratum spinosum are steadily formed.
At 48 hours, a new layer of skin can be seen, and at 120 hours, a new upper layer of skin is visible.
As these new cells develop, the fluid is reabsorbed and the swelling subsides.
Painful blisters on the palm of the hands or soles of the feet are often caused by tissue shearing in deeper layers of the skin. These layers lie next to nerve endings, thereby producing more pain.
Most blisters will heal without medical intervention. As the new skin grows beneath the blister, the fluid will slowly disappear and the skin will naturally dry and peel off.
Blisters are best left intact to prevent infection of the affected area.
Popping blisters is not recommended, because the bubble is a protective layer that fends off infection.
Once the barrier is removed, the wound is open to potential invasion by bacteria and can become infected.
Covering the blister with a band-aid or gauze can help protect it from additional trauma while it heals.
If the blister bursts, resist the urge to peel off any dead skin on the top.
Allow the fluid to drain away naturally and carefully wash it with mild soapy water.
Cover the blister and the surrounding area with a sterile, dry dressing.
Some over-the-counter (OTC) medications, such as hydrocolloid dressings, can help prevent further discomfort and encourage the healing process.
Similarly, with blood blisters, allow them to heal under in their own time. They can be more painful than standard blisters and an ice pack can offer some relief. Place a towel over the affected area, ensuring that the ice pack does not come into contact with the skin directly.
Friction blisters are best prevented by removing the cause of the friction. This can be achieved in a number of ways.
Avoiding blisters on the feet
Wear well-fitted, comfortable footwear and clean socks. Badly fitted or stiff shoes, such as high heels, carry a higher risk of blistering. Moist skin blisters more easily, so socks that manage moisture or frequent sock changes can be helpful.
During exercise and sports, specially designed sports socks can reduce the amount of available foot sweat.
Adequately breaking in walking or hiking boots before embarking on a long trek is also important.
Applying tape, padding or moleskin to trouble spots can help prevent blisters from appearing. Even better are friction-management patches which are applied to the inside of shoes. These will remain in place longer, throughout many changes of socks or insoles.
Avoiding blisters on the hands
When using tools, carrying out manual work or playing a sport where holding a bat is necessary, wearing gloves will prevent the majority of blisters.
In some sports, such as gymnastics, weightlifting or rowing, taping up the hands is good practice. Additionally, talcum powder acts to reduce friction and can be used in combination with gloves and tape, or as a stand-alone option. But, because talcum powder absorbs moisture, it will not work well for long durations of activity.
Although blisters are a painful annoyance, they do not typically signify any medical issues. By following a few of the basic rules above, blisters can often be prevented.