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.
Blisters are small raised areas that are filled with fluid and located in the superficial layer of the skin. They look like bubbles on the surface of the skin. Although they are often caused by irritation or friction (such as with a poorly fitting shoe), blisters can also represent disease processes. Blisters can accompany some types of skin rashes and inflammatory conditions, including certain autoimmune diseases. Depending upon the cause of the blisters, blisters may occur singly or in groups. In contrast to abscesses and boils, which are collections of inflammatory fluid found deep in the tissues, blisters are found in the most superficial layer of skin.
If a blister isn’t too painful, try to keep it intact. Unbroken skin over a blister may provide a natural barrier to bacteria and decreases the risk of infection. Cover it with an adhesive bandage or moleskin. Cut a piece of moleskin into a doughnut shape and place the pad so that it encircles and protects the blister. Then cover the blister and moleskin with gauze.
Depending on the cause and location, a blister can range from the size of a pinprick to three centimetres or more in diameter. A blood blister is usually caused by a severe pinch or bruise to the skin that breaks the tiny blood vessels (capillaries).
What Are Blisters?
A blister is a collection of clear fluid trapped within or beneath the top layer of skin, the epidermis. Blisters, which are often called “water blisters,” often break open and the fluid inside is released onto the skin. A blood blister is a specific type of blister when blood and other fluids pool under the skin. Blisters, also known as vesicles, can occur in all age groups and populations.
In contrast to a blister, an abscess is a collection of pus—a thick, cloudy, white or yellow-colored fluid that contains white blood cells and dead tissue. An abscess is caused by the body’s response to an infection (usually a bacterial infection). A blister that becomes seriously infected can develop into an abscess.
Blisters can be caused by a wide variety of mild to serious diseases, disorders and conditions, including infection, inflammation, autoimmune disorder, trauma, allergy, adverse drug reaction, and other abnormal processes. Blisters can form anywhere on the body, including inside the mouth, nose and genitals. Blisters can occur in isolation or you may develop hundreds of tiny blisters that affect several areas of the body. Blisters can be very tiny and hardly noticeable or quite large, reaching a quarter inch in diameter or larger.
Depending on the cause, a blister can go away suddenly, such as a friction blister that develops from wearing a new pair of shoes. Blisters that occur unexpectedly, worsen over time, or occur in large numbers may be a sign of a more serious condition, such as an autoimmune or infectious disease. Diseases that cause blistering of the skin are called bullous skin diseases.
Because a blister can be a sign of a serious disease or condition, you should seek prompt medical care and talk with your medical professional about a blister or blisters that are persistent or occur with swollen lymph nodes, fever, pain, joint achiness, or the development of pain, redness or pus.
Signs and Symptoms
Blisters typically develop on the soles of feet and the palms of hands when there is friction and irritation on the surface layer of the skin.
Depending on the severity as well as the stage of the blister, the appearance may vary.
- Early stage blisters – redness of the skin on the affected area, such as on the heel, the instep, toes, or palms.
- Mild, middle stage blisters – the affected area forms into a bubble-like swelling under the skin. The fluid is clear.
- Moderate or severe, middle stage blisters – the affected area forms into a bubble-like swelling under the skin and may be quite large. Infected blisters look red around the edge, and the fluid is often pus-like or red. Additionally, infected blisters are painful and warm to the touch.
- Late stage blisters – as the blister heals, the skin on the blister dries and typically sloughs off naturally, leaving healthy skin underneath.
There are many activities and ailments that can induce blistering. Below are some of the more common ways that blisters can form.
Friction blisters, named for what causes them, are one of the most common kinds. Think back. Have you ever worn a new pair of hiking boots before you broke them in? Or raked the yard without a pair of garden gloves on your hands? Those are the kinds of things that could cause a friction blister on your heel, toe, thumb, or palm.
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
Rub up against a pesky plant like poison ivy, and you might end up with blisters of another sort. They’re often a symptom of contact dermatitis, which happens when you touch something you’re allergic to. It doesn’t have to be poisonous, though. Some people react to soap, perfume, detergent, fabric, jewelry, latex gloves, or things used to make tools, toys, or other everyday objects.
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.
Insects can take the blame for some itchy blisters. Scabies are tiny mites that drill into your skin, sometimes leaving curved lines of blisters in their tracks. They often attack the hands, feet, wrists, and under the arms. Flea and bedbug bites can cause little blisters, too. The brown recluse spider has an extra-nasty bite that blisters before bursting to form a painful open sore. If that describes your blister, go to the doctor right away.
This disease is named after the blisters it causes on these body parts. The infection mostly hits kids younger than 10. The virus spreads through contact with mucus, saliva, feces, or blisters of someone who’s already sick. The infection starts out with a mild fever, runny nose, and sore throat. But the blisters are the big clue that leads to a diagnosis.
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.
How Are Blisters Diagnosed?
Healthcare providers can often diagnose blisters by looking at your skin. If your provider thinks you may have an infection or a skin disorder, a blister biopsy may be done. A piece of the blister is removed and checked under a microscope. Or a skin culture may be needed.
The goal of blister treatment is to protect the blister to prevent it from bursting. This allows the skin underneath the blister to heal properly and prevent infection.
Blisters are more often a nuisance than a serious medical problem. By knowing proper at-home remedies, you can find safe relief from blister pain and watch for the symptoms that signal when it’s time to see your doctor. Contrary to a popular myth, do not put butter on your blister. It seals in heat and increases the risk of infection.
Treating Common Blisters
Almost everyone has had a blister at some point. Common causes of blisters include ill-fitting or new footwear, friction from using tools such as a garden hoe or hammer, or minor burns such as spilling hot water on yourself.
Whatever the cause, doctors usually advise that you don’t touch the blister if possible. The outer layer is protecting the wound underneath and popping a blister exposes this wound to germs that could lead to infection.
If the blistered area is not exposed to further friction and can be kept clean, you may want to leave it uncovered. However, if it is in an area that may be exposed to more friction or in a spot where you can’t keep it clean, cover the blister with a dry, loose bandage. Don’t pull the bandage tight like you might when you cover a cut. Instead, leave the bandage a bit tented to give the blister some space. As the blister heals, the fluid will get reabsorbed into the body and the blister will flatten. The blistered tissue will eventually dry out and fall or peel off.
You can also protect the blister with a piece of moleskin, available under various brands at pharmacies and drug stores. Cut a piece larger than the blister itself. Cut a hole in the center of the moleskin slightly larger than the blister. Gently apply the moleskin to your skin. Cover both the blister and moleskin with a loose bandage.
If the blister breaks on its own, you should gently clean the area with soap and water and protect it with a bandage.
Blisters caused by burns may need medical treatment.
Treating Blisters Caused By Skin Conditions
If your blister is caused by a skin condition, such as eczema, speak with your doctor about treatments should the blisters recur. You may need to apply corticosteroid cream or other medication.
Treating Fever Blisters (Cold Sores)
You may have heard the term “fever blister” before, but these are not the same thing as having a fever when you have a blister, which can be a sign of infection. Fever blisters, or cold sores, are caused by a viral infection. They are made up of many tiny blisters all clustered together. It’s important not to pick at these because the virus can be easily spread.
You can shorten healing time and reduce symptoms of a cold sore breakout with over-the-counter topical medicine. Your doctor can also prescribe antiviral pills to shorten or prevent outbreaks.
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. These products are available for purchase online. 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.