Blisters form in response to friction or pressure on the skin. You can usually look after them yourself and many don’t need treatment at all. Some blisters are more serious or may be a symptom of disease and, in this case, they should be treated by a doctor.

What is a blister?

A blister is a small bubble of fluid, often clear, under the top layer of skin. It forms when friction repeatedly stretches the skin, creating a tear between skin layers, which fills with fluid. A hard knock that damages blood vessels can cause a blood blister, which is simply a blister filled with blood.

The pressure of fluid in the blister can be painful.

Depending on their cause, blisters can occur on the feet, hands, lips, mouth, torso or genital areas.

What causes blisters?

Blisters are commonly caused by friction or pressure, such as when new shoes repeatedly rub your heel.

Blisters can also be caused by injuries or damage from:

• insect bites or stings
• scalds or burns
• sunburn
• frostbite
• chilblains
• pressure ulcers (bedsores)
• contact with irritants that cause contact dermatitis, such as primula plants or the metal nickel

Some diseases and infections can also cause blisters, including:

• chicken pox
• shingles
• hand, foot and mouth disease
• impetigo or, 'school sores'
• cellulitis
• genital herpes
• cold sores
• autoimmune diseases, such as pemphigus
• inherited diseases, such as epidermolysis bullosa

When should I see my doctor?

You should seek medical help if:

• you think your blister might be caused by a disease or infection — for example, if several blisters form without an obvious cause
• you have a blister on your mouth, eye or genitals
• you have blisters after a serious burn or sunburn
• your blister looks infected (it is full of pus, is inflamed and is painful)
• you have diabetes or circulation problems

How are blisters treated?

Serious blisters, and those caused by disease or infection, should only be treated under the direction of a doctor. You might need antibiotics or other medication to treat the underlying condition.

A minor blister that hasn’t burst will dry up in a week or 2. If possible, leave it alone to heal. The covering skin protects the blister from infection.

If you think the blister might burst, cover it with a loose bandage.

Cut a padded dressing into a doughnut shape (with a hole in the middle) and place it around the blister. Then, cover the blister and padding with a bandage.

If a blister has burst, wash and clean it. Leave the roof of the blister on and cover it with a plaster or bandage. A blister that has lost its roof completely can be covered with a special blister plaster. A pharmacist can advise you about this.

Don’t use home remedies such as green tea or vinegar because they are not effective.

You might decide to puncture a blister to drain the fluid if it is large and painful, but take care to avoid infection. To drain a blister: 

• thoroughly wash your hands and the blister
• sterilise a clean needle with rubbing alcohol
• pierce the edge of the blister and let the fluid drain out
• wash the blister again
• apply an ointment, such as petroleum jelly
• cover with a bandage

Can blisters be prevented?

To prevent friction blisters, you can:

• wear shoes that don’t rub
• wear moisture-wicking socks
• wear gloves when digging or gardening
• cover friction ‘hotspots’ with hypoallergenic adhesive tape (again, your pharmacist can advise you) or use anti-friction skin balm

Resources and support

• For blister first aid, visit the St John Ambulance website.
• If you have a rare autoimmune or hereditary blistering disease, you can contact the Australasian Blistering Diseases Foundation.