Medically Reviewed By William C. Lloyd III, MD, FACS
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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.

If you have diabetes, you should seek prompt medical care to evaluate any blisters on the feet or legs, even if they are small.

Seek immediate medical care (call 911) if you have blisters with a high fever (higher than 101°F), difficulty breathing, a severe or electrical burn, or you have been exposed to cold temperatures or toxic chemicals, such as lye or acids.

What are the different types of blisters?

Blisters generally fall into three main types of blisters:

  • Friction blister. A friction blister (“water blister”) is a collection of clear, colorless fluid trapped between or beneath the top layer of skin, the epidermis. Water blisters typically form when skin rubs against a surface, causing friction. Burns, frostbite or infections can also cause water blisters.
  • Blood blister. A blood blister is a specific type of blister due to damage to blood vessels and tissues just under the skin, which causes blood and other fluids to pool and form a bump. Blood blisters typically form after a strong pinch of the tissues, but there are other causes as well.
  • Heat blister. A heat blister (burn blister) forms over skin that has suffered a mild to severe burn from heat or chemical exposure. It’s important to protect a burn blister while the skin underneath heals. Bursting a burn blister can lead to infection.

Other blister types are named after the underlying condition that causes the blister, such as shingles, chickenpox, eczema, autoimmune diseases, and cold sore or fever blisters (from oral herpes). Diseases that cause blistering of the skin are called bullous skin diseases.

What are the symptoms of blisters?

When a blister forms, fluid builds up under the top layer of your skin and produces a bubble. Usually the fluid is colorless, but in some cases the blister is filled with blood (blood blister) or pus if there is an infection.

Other symptoms that may occur with blisters

Blisters may occur with other symptoms, which vary depending on the underlying disease, disorder or condition. Common symptoms can include a burning sensation, pain, rash and itching. Potential symptoms that may accompany a blister include:

  • Burning sensation
  • Pain or tenderness around the blister
  • Itching
  • Rash
  • Tingling sensation before visible blister
  • Joint pain
  • Swollen lymph nodes

Serious symptoms that might indicate a life-threatening condition
In some cases, a blister or group of blisters can indicate a serious or life-threatening condition that should be immediately evaluated in an emergency setting.

Seek immediate medical care (call 911) if you, or someone you are with, have blisters with any of these life-threatening symptoms or conditions including:

  • Change in level of consciousness or alertness, such as passing out or unresponsiveness
  • Electrical injury
  • Exposure to a toxic chemical, such as lye or acids
  • Exposure to cold temperatures (possible frostbite and hypothermia)
  • High fever (higher than 101°F)
  • Redness, increased pain, pus, and warmth of affected area
  • Respiratory or breathing problems, such as shortness of breath, difficulty breathing, labored breathing, wheezing, not breathing, or choking

In addition, if you have diabetes, seek prompt medical care to evaluate and treat any blister on the feet or legs—even a small blister, because of a high risk of serious infection.

What causes blisters?

A blister can be a symptom of a variety of disorders, diseases or conditions, including infection, inflammation, trauma, allergic reaction, and other abnormal processes. Blisters form due to microscopic changes to the walls of small blood vessels that permit clear serous fluid to escape the otherwise intact blood vessel and collect within nearby skin layers.

Some causes are relatively harmless, such as blisters on the feet from ill-fitting shoes or blisters on the hands from working with garden tools. Other conditions require prompt medical care, such as an infectious disease or scalding from boiling water.

Infections that cause blisters

Blisters can be caused by infectious diseases including:

  • Bacterial skin infection, such as cellulitis or impetigo, which are commonly caused by staphylococcal or streptococcal bacteria
  • Chickenpox (varicella-zoster virus infection)
  • Herpes simplex virus infection, which causes cold sores (fever blisters) and genital herpes
  • Infected hair follicle
  • Shingles (reactivation of the chickenpox virus)
  • Yeast or fungal infection

Trauma or injuries that cause blisters

Blisters can be due to irritation of the skin or trauma including:

  • Chafing or friction, such as from ill-fitting shoes
  • Chemical, electrical or heat burn
  • Radiation burn
  • Sunburn

Other disorders that cause blisters

Blisters can be due to a variety of other diseases, disorders, and conditions including:

  • Adverse drug reaction
  • Allergic skin reaction
  • Bullous pemphigoid (a possible autoimmune disorder)
  • Erythema multiforme (allergic reaction in response to a drug, infection, or other illness)
  • Paraneoplasia (benign skin changes indicating cancer elsewhere)
  • Pemphigus vulgaris or other bullous (blistering) diseases
  • Porphyria cutanea tarda (an enzyme deficiency)

What do blisters look like?

Friction blister on heal from chafing or friction, such as from ill-fitting shoes

Macro hematoma on a finger after being hit with a hammer.
Blood blister due to damage to blood vessels and tissues just under the skin
Blisters on hand
Water blisters on hand
Sunburn with blisters
Sunburn with water blisters
woman with second degree burn, burn blister on wrist
Second degree burn blister

shingles (herpes zoster) rash and blisters on hand
Blisters from shingles (reactivation of the chickenpox virus)
Close-up of cold sore on unseen Caucasian woman's lip
Oral herpes blister (cold sore)

How do you prevent blisters?

Depending on the cause, you may be able to prevent blisters by taking certain precautions or treating the underlying condition that can cause blisters from forming.

Preventing friction blisters

Most friction blisters can be prevented by taking some simple steps.

  • Ensure your shoes are well fitting. Your shoe size may change even as you age, so be sure to get remeasured every so often while shoe shopping. It’s also a good idea to buy shoes at the end of the day rather than at the start, as your feet may be a bit larger due to swelling throughout the day.
  • Don’t ignore the pain and rubbing from an object. If you’re using a rake in your garden, for example, and you start to feel a blister forming on your hand or thumb, put on a pair of gloves or cover the area with a bandage or moleskin. If your shoes are causing the blister, switch shoes or protect the affected area.
  • Reduce friction by using talc powder or petroleum jelly on vulnerable spots.

You may find that some parts of your body are more prone to blisters than others. Once you know this, you can take steps to reduce the chances of blisters forming.

Preventing burn blisters

You can prevent burn blisters by taking special precautions when handling hot surfaces, boiling water, and working with electricity. Protect your skin for exposure to chemicals. Apply sunscreen with SPF of at least 30 to protect skin from sunburns which can cause burn blisters.

For minor burns, you may be able to prevent a blister from forming by running cool water over the burn area for 10 minutes. Then gentle dry the area by patting the area with a clean soft cloth.

Preventing blisters due to other conditions

Blisters can be due to a variety of other diseases, disorders and conditions. Working with your doctor and following your treatment plan to manage these conditions can help prevent blisters from forming.

When should you see a doctor for blisters?

Most blisters heal well on their own but there are some situations that require medical attention. Here are some common signs it’s time to see a doctor for blisters:

  • You think there’s an infection.
  • You have a fever.
  • You are getting more blisters around the area.
  • The blisters formed because of a burn, frostbite, chemical burn, or some other injury or condition.

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.

People with poor blood circulation to the feet and those who have diabetes should see a doctor or diabetic care nurse if a blister forms on a foot or toe, or the lower leg, as this can signal a dangerous complication.

How do you treat blisters?

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.

Should you drain a blister?

Normally, doctors do not advise patients to pop blisters because this can lead to infection. However, there may be some situations in which popping a blister can relieve pain and pressure. Keep in mind, though, if you have diabetes or poor blood circulation in your feet, you should not pop a blister yourself and instead should contact your doctor.

If you do choose to pop a blister at home, follow these steps to drain it safely.

  • Wash your hands with soap and water, and dry thoroughly.
  • Gently wash the blister with soap and water. Pat dry gently; don’t rub.
  • Take a clean needle and wipe it with alcohol to sterilize it. Wait for it to dry.
  • Very gently, poke the needle into the blister on the edge, near the healthy skin. Do this a few times around the blister. Do not peel back the elevated dome of dead skin.
  • Allow the fluid to drain. If it looks like pus (white or yellow thick liquid), you may have an infection. Contact your doctor to determine if you need treatment.
  • Dry the area by patting it gently with a clean cloth. Dab a bit of petroleum jelly (sterile packet, if available) over the blistered area and cover it loosely with a bandage. Keep it clean and dry.
  • Check regularly for signs of infection, such as redness, increasing pain, and pus drainage.

What are the potential complications of blisters?

Complications associated with a blister can be progressive and vary depending on the underlying cause. Because blisters can be due to a serious disease, not seeking treatment can result in complications and permanent damage. It is important to contact your healthcare provider when you develop an unexplained blister or group of blisters, even if you do not have other symptoms.

Once the underlying cause is diagnosed, following the treatment plan outlined by your doctor can help reduce any potential complications including:

  • Permanent change in skin texture and scarring
  • Permanent skin discoloration
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Dec 19
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  2. Blisters (Overview). Harvard Health Publishing.
  3. How to Prevent and Treat Blisters. American Academy of Dermatology Association.
  4. Cold sore. Mayo Clinic.
  5. Vesicles. MedlinePlus, National Library of Medicine, National Institutes of Health.
  6. Bullous pemphigoid. MedlinePlus, National Library of Medicine, National Institutes of Health.
  7. Porphyria. U.S. National Library of Medicine.
  8. Weedon D. Weedon's Skin Pathology, 3rd ed, Philadelphia: Elsevier Limited, 2010.