Boils and carbuncles are red, painful lumps on the skin that are usually caused by a bacterial infection.
Symptoms of boils and carbuncles
Boils can develop anywhere on your skin. You're most likely to get one in an area where there's a combination of hair, sweat and friction. For example, the neck, face or thighs.
Over time, pus forms inside the boil, making it bigger and more painful. Most boils will burst and the pus will drain away without leaving a scar. This can take from 2 days to 3 weeks to happen.
Boils are relatively common in teenagers and young adults, usually in males.
It can sometimes be difficult to tell the difference between a boil and a spot. Boils tend to grow bigger and become more painful. Your GP should be able to diagnose a boil from its appearance.
A carbuncle is a cluster of boils that usually develops over a few days. The areas most commonly affected are the back, thighs, or back of the neck.
A carbuncle can grow to a size of 3cm to 10cm and will leak pus from different points.
You may also:
- have a high temperature of 38 degrees Celsius or above
- feel generally unwell
- feel weak and exhausted
Carbuncles are less common than boils. They mostly affect middle-aged or older men in poor health or with a weakened immune system.
Causes of boils and carbuncles
Boils and carbuncles are often caused by bacteria called staphylococcus aureus (staph bacteria). The bacteria infects one or more hair follicles. Staph bacteria usually live on the surface of the skin or in the lining of the nose without causing harm.
You can get a boil when bacteria enter the skin through cuts and grazes. Your immune system then sends infection-fighting white blood cells to kill the bacteria.
Over time, pus forms inside the boil. This is from a build-up of dead white blood cells, skin cells and bacteria.
A carbuncle develops when the infection spreads further beneath the skin. This creates a cluster of boils.
Preventing boils and carbuncles
You cannot always avoid getting a boil or carbuncle.
These tips can reduce your risk:
- wash your skin regularly using a mild antibacterial soap
- carefully clean any cuts, wounds or grazes - even small ones
- cover cuts, wounds and grazes with a sterile bandage until they heal
- healthy eating and regular exercise to boost your immune system
How boils and carbuncles are spread
Unlike acne, boils and carbuncles can spread to another part of the body or to another person.
To prevent boils and carbuncles spreading, take simple precautions such as:
- washing your hands after touching affected areas
- using a separate face cloth and towel
- washing underwear, bed linen and towels at a high temperature
- covering wounds with a dressing until they heal
- carefully disposing of used dressings
When to see your GP
See your GP if you think you have a carbuncle.
With boils, you do not usually need to see a doctor as most boils burst and heal by themselves.
See your GP if you have a boil:
- on your face, nose or spine – this can sometimes cause serious complications
- that gets bigger and feels soft and spongy to touch – it may not burst and heal by itself
- that does not heal within 2 weeks
- and you have a temperature and feel generally unwell
Your GP should be able to identify a boil or carbuncle by looking at it.
You may need further tests, such as a blood test or skin swab, if you have:
- a boil or carbuncle that keeps returning or doesn't respond to treatment
- many boils or carbuncles
- a weakened immune system - from a condition like diabetes or having chemotherapy