Blisters are fluid-filled swellings on the surface of your skin. They often occur in areas of the body such as the palms, fingers, heels and soles of the feet when they come into contact with objects that cause friction.
Some blisters are painless and some feel tender if pressure is applied. Blood blisters are dark in colour and are often more painful than other blisters. You may have a single blister or a group of blisters, depending on the cause.
As new skin grows under a blister, the fluid inside the blister is gradually reabsorbed and the outer layer of skin dries and peels off. This usually takes three to seven days.
Infection
If you have a blister that's infected, it will fill with pus, which may be yellow or green. The blister may be painful to touch. The skin around an infected blister may be red or there may be red streaks leading away from the blister. Your skin may also feel hot and painful.
It's important not to ignore an infected blister as it could potentially lead to secondary impetigo (a contagious bacterial infection of the skin) if it splits open (ruptures). This could lead to further complications such as cellulitis (a bacterial infection of the deeper layers of the skin) or sepsis (a life-threatening illness caused by the body overreacting to an infection).
When to seek medical attention
You should visit your GP if you have blisters that you think are infected or blisters that are very large, painful or reoccuring. Also visit your GP if you have blisters that develop in unusual places, such as on your eyelids or the inside of your mouth, or if they appear after contact with chemicals or other substances.
