Blisters

Skin and Nail Conditions· Also known as: foot blisters, friction blistersUpdated Oct 2026

Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, October 2026

At a Glance

A blister is a small pocket of fluid that forms in the upper layers of skin after it has been damaged. Blisters are most common on the hands and feet. On the feet, they usually come from repeated rubbing and shearing (skin layers sliding against each other), and they are very common in runners and hikers. You will see a tender, reddened patch of skin with a raised lump of fluid. Care is mostly about protecting the blister, keeping it clean and covered, and leaving the skin over it in place.

What is it?

A blister is a small pocket of fluid in the upper layers of damaged skin. Most are filled with clear fluid. A blood blister is filled with blood instead, so it looks red or black. A blister that becomes inflamed or infected can fill with pus.

Blisters can appear anywhere on the body, but they are most common on the hands and feet. Your body makes a blister to protect the damaged skin underneath while it heals.

A friction blister is a tear inside the top layer of your skin (the epidermis). The fluid takes a little while to collect. It is usually fully filled within about 2 hours.

Who does it affect?

Blisters can affect anyone, but they are especially common in people who are very active. Foot blisters have been recorded in 16 to 76 per cent of runners and 29 to 95 per cent of hikers. Military recruits and other people doing a lot of walking, running or carrying loads are also at higher risk.

People with diabetes need extra care. Diabetes can reduce feeling and blood flow in the feet, so you may not notice rubbing, pressure or a small injury until it has become a bigger problem.

Signs and symptoms

A blister usually looks like a reddened, tender patch of skin with a raised lump filled with clear fluid. Sometimes the fluid is blood.

A friction blister tends to develop in steps. The skin first turns red, then looks pale, then a small fold forms in the top layer of skin, and then the fold fills with fluid.

An infected blister looks and feels different. It can be hot and filled with green or yellow pus. The skin around it may be red, swollen and more painful. On brown or black skin, the redness can be harder to see, so look for heat, swelling, pus and increasing pain as well.

What causes it?

Foot friction blisters are caused by repeated shearing. This means the layers of your skin slide against each other, rather than something simply rubbing on the surface. Three things come together: movement of the bones in your foot, a high friction force, and many repeats of that movement.

Blisters can have other causes too. They include burns and scalds, sunburn, contact with chemicals such as detergent, allergic reactions, and conditions such as chickenpox and impetigo (a bacterial skin infection). Blisters can also come from a skin infestation of tiny mites called scabies, and cold sores cause small blisters on the lips or around the mouth.

How is it diagnosed?

A blister is usually obvious to look at. Your podiatrist will check the fluid (clear, blood or pus), the site, and any redness or warmth around it.

They will probably ask about your shoes, socks, how active you are, and whether anything has changed recently, such as a new pair of shoes or a sudden jump in walking or running. They will also ask about burns, sunburn, new products or medicines, and whether other blisters have appeared elsewhere.

If the blister doesn't look like a rubbing injury, your podiatrist or doctor will look for another cause.

Treatment

Care is mainly about protection. Your body made the blister to help the skin underneath heal, so the aim is to leave it in place where you can.

Looking after it at home

If the blister is intact, leave it alone and protect it from the shoe or equipment that caused it. Keep it covered. Where possible, don't burst it or remove its roof (the skin over the top), because that can lead to infection and slow healing. Don't peel or pick at the skin.

If the blister bursts by itself, let the fluid drain. Then cover it with a clean plaster or dressing.

If you have diabetes and find a blister or any break in the skin on your foot, cover it with a sterile dressing and don't burst it. Then contact your GP or podiatrist the same day, as set out under "When to see a podiatrist".

Treatment from your podiatrist

If a blister needs to be drained, your podiatrist will use only sterile instruments. The needle goes in parallel to the skin rather than straight down, so the base of the blister isn't damaged. They let the fluid escape slowly and keep the roof in place, where possible, so it acts as a natural dressing. They will then cover it with a dressing or plaster.

If the roof has already torn off or been removed, your podiatrist will usually apply a sterile dressing that won't stick to the raw skin, such as coated gauze. There is no single right way to treat every blister, because the best choice depends on the cause and on you.

Other options

If a blister is dirty or infected, your podiatrist or doctor may use special antimicrobial dressings or products for a time. These are not needed for a normal, intact friction blister.

For people with diabetes, well-fitting shoes matter. They should support the foot and avoid pressure points. It isn't yet clear whether shoe inserts (orthoses) help prevent blisters.

Recovery

The most useful things you can do are to keep the blister protected, stop it rubbing, and avoid the shoes or equipment that caused it while it heals. Bursting the blister or taking off its roof can slow things down. It isn't possible to give a reliable healing time, as it depends on the blister and on you.

If you have diabetes, a blister that isn't healing can become a more serious problem, because feet with reduced feeling and blood flow may not heal as easily. See your podiatrist for any blister that isn't healing. Foot problems in people with diabetes can get worse within hours, so check your feet every day.

Preventing it

Because blisters come from repeated shearing, prevention is about reducing that rubbing. Shoes and socks that fit well, and that don't leave pressure points, are a good start. If blisters keep coming back, review your socks and shoes. Your podiatrist can help with this.

It isn't yet clear which type of sock or product works best. People who have run long races before tend to get fewer blisters, so building up your activity gradually is sensible.

If you have diabetes:

Check your feet every day, and act on any change straight away.
Choose shoes that fit well, support your feet and avoid pressure points.
Test bath or wash water with your elbow, or ask someone else to test it, because you may not feel heat.

When to see a podiatrist

Book an appointment if

A blister isn't healing, or you keep getting blisters from your activity or footwear and want help with shoes, socks and protection. If you have diabetes, a blister that isn't healing needs a podiatrist.

Seek prompt assessment if

Call your local emergency number if you have an infected blister and you also feel very unwell, with confusion or slurred speech, severe shivering or muscle pain, severe breathlessness, mottled or discoloured skin, or little or no urine. This could be sepsis. See your GP or another doctor today if you have diabetes and you find a blister or a break in the skin on your foot, or your foot is red, warm or swollen, has a discharge, or you feel unwell. Foot problems can get worse within hours when you have diabetes, and you may not feel pain even with a wound. If your GP can't see you today, go to an urgent care clinic or an after-hours GP. See your GP soon if the blister looks infected (hot, filled with green or yellow pus, or with increasing swelling, redness or pain, though redness is harder to see on brown or black skin), because an infection left untreated could spread to the skin or blood. See your GP soon too if the blister came from a burn, scald, severe sunburn or an allergic reaction, if it is very painful or keeps coming back, if it is on your eyelids, mouth or genitals, if several blisters have appeared with no obvious cause, or if you have circulation problems.

Frequently asked questions

What is a blood blister?

A blood blister is filled with blood instead of clear fluid, so it looks red or black. It involves damaged blood vessels as well as damaged skin. Like other blisters, it is best left intact, kept covered and protected from more rubbing.

How long does a blister take to heal?

A reliable healing time can't be given, because it varies from blister to blister. What helps most is stopping the rubbing, keeping the blister covered and leaving the roof in place. If a blister isn't healing, book an appointment with your podiatrist.

Do blister plasters or special socks work?

It isn't yet clear which type of plaster, sock or product works best. What matters most is that your shoes and socks fit well and don't create pressure points or rub. If blisters keep coming back, your podiatrist can look at your footwear with you.

Can a blister be something other than rubbing?

Yes. Burns, scalds, sunburn, chemicals, allergic reactions and some infections and skin conditions can all cause blisters. A blister with no clear rubbing cause, or several blisters appearing at once, is worth having checked by your GP.