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General health information

Blisters

A blister is a fluid-filled pocket beneath the top layer of skin. Friction, a burn, an allergy or a skin condition may cause it; most blisters heal on their own if protected.

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  • A blister is a pocket of clear fluid or blood between skin layers. Friction is the most common cause, but heat, cold, chemicals, infections, skin conditions and medicines can also cause blisters.
  • A small, intact friction blister usually heals within about a week. Leave the skin covering it in place: it is a natural barrier against dirt and bacteria.
  • Stop the friction, keep the area clean and dry, and cover with a soft plaster or clean dressing if needed.
  • Do not routinely burst a blister yourself. A large, tense or very painful blister can sometimes be drained under sterile conditions by a healthcare professional.
  • Watch for increasing redness, warmth, swelling, pus, an unpleasant smell, throbbing pain, fever or a red streak: these may indicate infection.
  • Take extra care if you have diabetes, poor circulation, nerve damage or reduced immunity. Have a foot blister assessed early in these cases.
  • Several blisters without clear friction, or blisters in the mouth, eyes or genitals, need medical assessment.

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Further reading

Browse A–Z
A
Aphthous mouth ulcersAphthous ulcers are small, painful sores inside the mouth. Most heal on their own within one to two weeks and are not contagious.
C
Contact dermatitisContact dermatitis is skin inflammation caused by direct irritation or a delayed allergic reaction to a substance. The skin may itch, burn, become red or darker, and develop blisters, cracks and scaling. The main step is to identify the cause and limit contact, while restoring the skin barrier and using treatment if needed.
C
Central serous chorioretinopathyA 'fluid blister in the retina' often means central serous chorioretinopathy: fluid leaks from the vascular layer beneath the central retina and lifts the macula locally. It often resolves by itself, but recurrence or prolonged fluid can cause permanent loss of contrast and detail; many sudden flashes, floaters or a curtain over vision are not a reason to wait and see.