Boils and carbuncles are red, painful lumps on the skin.
Boils (furuncles) can develop anywhere on your skin, but they’re most likely to occur at the site of an infected hair follicle (a hole a hair grows out of).
Boils most commonly develop on areas of skin where there’s a combination of hair, sweat and friction, such as the neck, face or thighs.
Over time, pus forms inside the boil, causing it to grow larger and become more painful. In most cases, a boil will eventually burst and the pus will drain away without leaving a scar. This can take from two days to three weeks to happen.
Boils are more common in teenagers and young adults, especially in males. Young males living in overcrowded and possibly unhygienic conditions are particularly at risk.
A carbuncle is a dome-shaped collection of boils that usually develops over the space of a few days. They most often occur on the back, thighs, or the back of the neck.
A fully grown carbuncle can be more than 10cm (4 inches) in size, and will leak pus from a number of points.
You may also have other symptoms, such as:
- a high temperature of 38C (100.4F) or above
- a general feeling of being unwell
- feeling weak and exhausted
Carbuncles are less common than boils and tend to occur mostly in middle-aged or older men in poor health or with a weakened immune system.
When to see your GP
Most boils burst and heal by themselves without the need for medical treatment. However, visit your GP for advice 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 doesn’t heal within two weeks
You should also see your GP if you develop a carbuncle, or if you have additional symptoms such as a high temperature or feeling generally unwell.
You GP should be able to identify a boil or carbuncle by looking at it.
Causes of boils and carbuncles
Boils and carbuncles are often caused by a type of bacteria known as Staphylococcus aureus (staph bacteria) infecting one or more hair follicles. Staph bacteria usually live harmlessly on the surface of the skin or in the lining of the nose.
Boils tend to occur when the bacteria enters the skin through cuts and grazes. This causes your immune system to respond by sending infection-fighting white blood cells to kill the bacteria.
Over time, a mix of dead bacteria, dead white blood cells and dead skin cells builds up inside the boil to form pus.
A carbuncle develops when the infection spreads further beneath the skin to create a cluster of boils.
Can I catch a boil or carbuncle?
Yes, you can. Unlike acne, both boils and carbuncles can spread to another part of the body or to another person.
Taking simple precautions, such as carefully disposing of used dressings and washing your hands after touching affected areas of skin, can help prevent boils and carbuncles spreading.
Treating boils and carbuncles
Most boils can be treated at home. One of the best ways to speed up healing is to apply a warm face cloth to the boil three or four times a day.
If your boil doesn’t heal, your GP may decide to drain it.
Never attempt to squeeze or pierce a boil or carbuncle because it could cause the infection to spread and may lead to complications.
If you develop a carbuncle or there’s a high risk of your boil causing complications, you may be prescribed a week-long course of antibiotics.
Further testing, such as taking a skin swab or a blood test, may be required if you have:
- a boil or carbuncle that keeps returning or doesn’t respond to treatment – it may be caused by bacteria other than staph bacteria, so an antiseptic solution may be prescribed
- multiple boils or carbuncles
- a weakened immune system caused by a condition such as diabetes, or if you’re having a treatment such as chemotherapy
Read more about treating boils and carbuncles.
Although most boils get better without causing further problems, some people develop a secondary infection.
This can range from a relatively minor (though often very painful) infection of the deeper layer of the skin, such as cellulitis, to rarer and more serious infections, such as blood poisoning (sepsis).
Larger boils and carbuncles can also lead to scarring.
Complications are more likely to occur if boils and carbuncles aren’t treated properly.
Read more about the possible complications of boils and carbuncles.
Treating boils and carbuncles
Most boils get better without the need for medical treatment and can be successfully treated at home.
One of the best ways to speed up the healing process is to apply a warm face cloth to the boil for 10 minutes three or four times a day. The heat increases the amount of blood circulating around the boil, which means more infection-fighting white blood cells are sent there.
When the boil bursts, cover it with sterile gauze or dressing to prevent the spread of infection. After this, wash your hands thoroughly using hot water and soap. This will help prevent you spreading bacteria to other parts of your body or other people.
See your GP if you have a larger boil that feels soft and spongy to the touch (the medical name for this is a fluctuant boil).
Once a boil becomes soft and spongy, it’s unlikely to burst open by itself and probably won’t respond well to treatment with antibiotics.
Your GP may be able to remove the pus using a technique called incision and drainage. In some cases, your GP may refer you to your local hospital for this treatment.
Incision and drainage involves piercing the tip of the boil with a sterile needle or scalpel. This encourages the pus to drain out of the boil, which should help to relieve pain and stimulate the recovery process.
Before having the procedure, it’s likely you’ll be given a local anaesthetic to numb the affected area.
Never attempt to squeeze or pierce a boil yourself because this can spread the infection.
Antibiotics are usually recommended:
- for all cases of carbuncles
- if you have a high temperature
- if you develop a secondary infection, such as cellulitis (an infection of the deeper layer of the skin)
- if you have a boil on your face – facial boils have a higher risk of causing complications
- if you’re in severe pain and discomfort
A seven-day course of a penicillin-based antibiotic called flucloxacillin is usually recommended. If penicillin is unsuitable for you, alternative antibiotics, such as erythromycin and clarithromycin, can be used.
It’s important to finish the course of antibiotics even if the boil goes away, otherwise the infection could return.
Treating recurrent boils and carbuncles
Boils and carbuncles that keep returning often need further treatment.
Most people with recurrent boils develop them because they’re carriers of Staphylococcus aureus bacteria (staph bacteria). In this case, treatment may be necessary to kill these bacteria.
Treatment depends on where the staph bacteria are found on your body. Bacteria on the skin can be treated with antiseptic soap. Staph bacteria in the nose will need to be treated with a prescribed antiseptic cream for up to 10 days.
Complications of boils and carbuncles
Although most boils don’t cause further problems, this isn’t always the case.
Scarring can sometimes occur after a larger boil or carbuncle. These scars never disappear completely, but they do fade with time and become less noticeable.
If you’re particularly concerned about scars, there are a number of treatments, including:
- corticosteroid injections, which can help flatten a raised scar
- pressure dressings, which can help flatten and soften a scar
- plastic surgery
However, it’s unlikely your local clinical commissioning group (CCG) will fund these treatments unless it can be shown your scars are causing you considerable psychological distress.
A simpler alternative is to use make-up to conceal any scars you have. Camouflage make-up specially designed for covering scars is available over the counter at pharmacies.
Read more about treating scars.
Spread of infection
The bacteria inside a boil or carbuncle can sometimes spread to other parts of the body and trigger a secondary infection.
Cellulitis (an infection of the deeper layers of skin) is the most common secondary infection associated with boils and carbuncles.
Less common secondary infections include:
- impetigo – a highly contagious skin infection that causes sores and blisters
- septic arthritis – an infection of a joint
- osteomyelitis – an infection that develops inside a bone
- endocarditis – an infection of the inner layer of the heart
- septicaemia – an infection of the blood
- brain abscess – a collection of pus that develops inside the brain
Some of these secondary infections need to be treated with antibiotic injections. In the case of septicaemia and brain abscess, you will be admitted to an intensive care unit (ICU).
Cavernous sinus thrombosis
Cavernous sinus thrombosis is a very rare but potentially life threatening complication of a boil. It occurs when an infection triggers a blood clot in the spaces behind the eye socket. The clot begins to increase the pressure on the brain, causing symptoms such as:
- a sharp and severe headache
- swelling of the eyes
- eye pain that’s often severe
Without prompt treatment with antibiotics, cavernous sinus thrombosis can be fatal. However, this condition is very rare.
Read more about cavernous sinus thrombosis.
Preventing boils and carbuncles
It’s not always possible to prevent getting a boil or carbuncle, but some simple steps can reduce your risk.
- washing your skin regularly using a mild antibacterial soap
- always carefully cleaning any cuts, wounds or grazes, even if they look very small
- keeping cuts, wounds and grazes covered with a sterile bandage until they heal
- eating a healthy diet and taking regular exercise to boost your immune system – this makes you less likely to develop skin infections, such as boils
For further information and advice regarding diet and exercise, see:
Preventing your boil or carbuncle from spreading
If you develop a boil or carbuncle, it’s important to prevent spreading the infection to other parts of your body or to other people. You can do this by:
- washing your hands with an antibacterial soap after touching a boil or carbuncle
- washing underwear, bed linen and towels at a high temperature
- using a separate face cloth and towel
- keeping any wounds covered with sterile gauze until they heal
- regularly changing the gauze covering a boil or carbuncle
- sealing used gauze or dressings in a plastic bag and throwing it in the dustbin immediately
- avoiding saunas, gyms and swimming baths until your skin has healed