Blisters are small pockets of fluid that usually form in the upper layers of skin after it's been damaged. Blisters can develop anywhere on the body but are most common on the hands and feet.
Fluid collects under the damaged skin, cushioning the tissue underneath. This protects the tissue from further damage and allows it to heal.
Most blisters are filled with a clear fluid (serum), but may be filled with blood (blood blisters) or pus if they become inflamed or infected.
Most blisters heal naturally after three to seven days and don't require medical attention.
It's important to avoid bursting the blister, because this could lead to an infection or slow down the healing process.
If the blister does burst, don't peel off the dead skin. Instead, allow the fluid inside the blister to drain and cover the area with a dry, sterile dressing to protect it from infection until it heals.
Read more about treating blisters.
When to see your GP
See your GP if you have blisters that:
- you think are infected
- are very painful
- keep coming back
An infected blister will be filled with yellow or green pus and may be painful, red and hot.
It's important not to ignore an infected blister because it could lead to secondary impetigo (a contagious bacterial infection of the skin) and further complications, such as cellulitis or sepsis.
You should also talk to your GP if you have blisters in unusual places, such as on your eyelids or inside your mouth, or if they appear after severe sunburn, burns or scalds or an allergic reaction, or after coming into contact with chemicals or other substances.
What causes blisters?
Blisters can be caused by:
- friction to the skin
- heat – for example, from sunburn or a scald
- contact with chemicals, such as detergent
- medical conditions, such as chickenpox and impetigo
Read more about what causes blisters.
There are a number of things you can do to avoid getting blisters caused by friction, sunburn or chemicals. For example, you can:
- wear comfortable, well-fitting shoes
- help keep your feet dry with thicker socks or talcum powder
- wear gloves when handling chemicals
- use sunscreen
Read more about preventing blisters.