What Causes A Blister? Prevention and Treatment

By Craig Sorkin, DNP, APN
Medically reviewed checkmarkMedically reviewed
July 19, 2022

A blister is a fluid-filled sac that forms under the outer layer of your skin. 

Most of the time, blisters form from friction, like wearing an ill-fitting shoe or not wearing a glove when shoveling or raking leaves.

Other causes such as burns, blood blisters, and several medical conditions can also cause blisters.

Typically, blisters are not a serious condition and can be treated at home.

In this article, I’ll explain more about blisters and what causes them.

I’ll also talk about proper treatment and how you can prevent blisters from forming.

Lastly, you’ll learn when you should have a blister checked by a medical professional.

What Are Blisters?

Your skin consists of three layers.

Blisters form when fluid collects under the first layer of skin.

This fluid formation creates a little sac filled with fluid that bubbles up from the skin layer. 

Sometimes it’s tempting to pop a blister, but it’s best to leave it intact.

The outer skin layer protects the deeper layer of skin and can prevent an infection from forming.

The medical term for a small blister is a vesicle, and a large blister is called a bulla.

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The most common cause of blisters is friction on the hands or feet.

Other causes include heat, chemical exposure, blood blisters, and medical conditions. 

Types of Blisters 

Read on to learn more about the cause and types of blisters. 


A blister can form in the skin anytime there is friction or pressure against it for a continuous period of time.

Examples could be wearing new shoes or ill-fitting shoes that rub on your feet in new areas.

Sometimes blisters also form on the hands when you don’t wear gloves while doing certain activities such as using tools or lifting hand weights.


A burn damages the skin from heat, sunlight, radiation, or electricity.

The most common burns are from hot liquids, steam, flammable liquids and gas, and building fires.

There are three types of burns:

  • First-degree burns involve damage to the outer layer of the skin
  • Second-degree burns damage the outer layer and second layer
  • Third-degree burns damage the deepest third layer of skin and other tissues beneath it 

A sunburn is caused by damage to the skin from ultraviolet (UV) rays.

A sunburn is a visible sign of skin damage and can happen during any season or temperature, so keep your skin protected.

Burns can cause blistering, swelling, scarring, and even shock and death in severe cases.

However, most minor burns can be cared for at home and don’t require medical treatment.

Chemical exposure

A chemical burn results from exposure to a caustic substance found in the home, workplace, or environment.

Direct spills or exposure burns can cause blistering on the skin. 

Common causes of chemical burns include:

  • Acids such as acetic acid, nitric, and phosphoric
  • Bases such as calcium hydroxide, ammonia, and sodium carbonate
  • Oxidants such as bleaches and peroxides
  • Miscellaneous things like hair coloring agents, metals, and airbag injuries

Young children learning to crawl and walk tend to get chemical burns from cleaners.

For this reason, be careful not to leave cleaning agents and other harmful substances under sinks and in low areas where children can accidentally get into them.

The degree of damage depends on the strength of the chemical, where the contact was on the body, and the length of exposure. 

Blood blister

A blood blister is similar to a friction blister, but it contains blood rather than clear fluid.

The reason for the blood is that a blood vessel broke during the injury.

A blood blister can result from friction or injury, like pinching your hand in a door. 

The blister may be painful, but it’s best to keep it clean, covered, and left alone.

There is no need to pop a blood blister.

It usually takes about one week for them to heal.

Medical conditions

Some medical conditions can cause blisters to form on the skin as well:

  • Cold sores, caused by a virus, are small blisters that form around the mouth or on the lips.
  • Genital herpes is a sexually transmitted infection (STI) caused by a virus and usually affecting the groin.
  • Hand, foot, and mouth disease is a viral infection that causes blisters to form on the hands, feet, and mouths of children.
  • Chickenpox is a viral disease, usually in children, that causes itchy blisters to form on the skin.
  • Skin infections caused by bacteria such as bullous impetigo, cellulitis, and MRSA.


Blisters will typically heal independently without medical intervention within a couple of weeks. As best as you can, try to be patient with your blister and leave it alone.

Be sure not to do the activity that caused the blister until it’s completely healed.

Dermatologists recommend the following treatment for blisters:

  • Cover the blister loosely with a bandage.
  • Use padding to protect any blisters that are in areas of high pressure, such as your feet. First, cut the padding so there is a hole in the middle (like a donut) and place it around the blister. Then cover the padding and blister with a bandage.
  • Avoid popping the blister. The outer layer of skin helps prevent infection and protects the skin layer underneath while it heals. 
  • Very large and painful blisters sometimes need to be drained. Consult your medical provider for guidance to ensure you’re protecting yourself from an infection or improper technique. 

During the healing process, watch for signs of infection such as redness, increased pain or swelling, and pus.


To prevent blisters from forming, take the following precautions:

  • Wear clothes that fit correctly and are the right type for your activity. For example, wear clothes that are moisture-wicking during physical activity to help keep your skin dry.
  • To prevent blisters on your feet, wear moisture-wicking or nylon socks and ensure your shoes fit correctly.’
  • Consider putting soft bandages on areas that may be tender or easy to blister.
  • Stop your activity or change your shoes immediately if you experience discomfort or pain or if your skin is turning red.

Use talcum powder in your socks if you tend to have sweaty feet.

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When To Seek Medical Attention

Blisters will generally heal on their own, but there are some cases in which a blister needs medical treatment. 

See your primary medical provider for the following:

  • A blister keeps coming back and is very painful
  • There are signs of infection such as redness, swelling, warmth, and yellow or green pus
  • The blister is in a delicate area such as the eyes, mouth, or genitals
  • You have several blisters for no known reason
  • Your blister is because of exposure to a chemical, allergic reaction, or scalding burn

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Is it better to pop a blister or leave it?
Generally, it’s better to leave a blister intact. This is because the top layer of skin protects the blister from infection and allows the lower layers of skin to heal. Very large or painful blisters sometimes need to be drained. Consult your medical provider for guidance to ensure you’re protecting yourself from an infection or improper technique.
What causes a blister?
Blisters are usually caused by friction or rubbing on the skin. However, burns, exposure to chemicals, and some medical conditions like bacterial skin infections can also cause blisters.
How do blisters heal?
Blisters heal from the inside out. The body will reabsorb the fluid, and the lower layers of skin with heal. The healing process typically takes about 1-2 weeks.
What is the best way to treat a blister?
Blisters should be kept clean, dry, and covered. Use a bandage to loosely cover the blister.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Craig Sorkin, DNP, APN

Craig Sorkin, DNP, APN is a board certified Family Nurse Practitioner with over 15 years experience. He received his Undergraduate and Graduate degrees from William Paterson University and his doctoral degree from Drexel University. He has spent his career working in the Emergency Room and Primary Care. The last 6 years of his career have been dedicated to the field of digital medicine. He has created departments geared towards this specialized practice as well as written blogs and a book about the topic.

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