An abscess is a painful collection of pus, usually caused by a bacterial infection.
An abscess can develop anywhere in the body. This article focuses on two types of abscess:
skin abscesses – which develop under the skin
internal abscesses – which develop inside the body, in an organ or in the spaces between organs
The symptoms of an abscess can vary, depending on which type you have.
A skin abscess often appears as a swollen, pus-filled lump under the surface of the skin. You may also have other symptoms of an infection, such as a high temperature (fever) and chills.
It's more difficult to identify an abscess inside the body, but signs include pain in the affected area, a high temperature and generally feeling unwell.
What causes abscesses?
Most abscesses are caused by a bacterial infection.
When bacteria enter your body, your immune system sends infection-fighting white blood cells to the affected area.
As the white blood cells attack the bacteria, some nearby tissue dies, creating a hole which then fills with pus to form an abscess. The pus contains a mixture of dead tissue, white blood cells and bacteria
Most skin abscesses are caused by bacteria getting into a minor wound, the root of a hair or a blocked oil or sweat gland. It may be possible to reduce your risk of skin abscesses through good hygiene, a healthy lifestyle and looking after your skin.
Internal abscesses often develop as a complication of an existing condition, such as an infection elsewhere in your body. For example, if your appendix bursts as a result of appendicitis, bacteria can spread inside your tummy (abdomen) and cause an abscess to form.
How abscesses are treated
A small skin abscess may drain naturally, or simply shrink, dry up and disappear without any treatment.
However, larger abscesses may need to be treated with antibiotics to clear the infection, and the pus may need to be drained. This will usually be done either by inserting a needle through your skin or by making a small incision in the skin over the abscess.
Other types of abscess
There are many other types of abscess not fully covered in this article, including:
an anorectal abscess – a build-up of pus in the rectum and anus
a Bartholin’s abscess – a build-up of pus inside one of the Bartholin’s glands, which are found on each side of the opening of the vagina
a brain abscess – a rare but potentially life-threatening build-up of pus inside the skull
a dental abscess – a build-up of pus under a tooth or in the supporting gum and bone
a quinsy (peritonsillar abscess) – a build-up of pus between one of your tonsils and the wall of your throat
a pilonidal abscess – a build-up of pus in the skin of the cleft of the buttocks (where the buttocks separate)
a spinal cord abscess – a build-up of pus around the spinal cord
Symptoms of an abscess
The symptoms of an abscess depend on where it develops in your body.
Signs of a skin abscess can include:
a smooth swelling under your skin that can feel hard or firm
pain and tenderness in the affected area
warmth and redness in the affected area
a visible build-up of white or yellow pus under the skin in the affected area
a high temperature (fever)
A boil is a common example of a skin abscess.
Abscesses that develop inside an organ or in the spaces between organs can be more difficult to identify than skin abscesses, because the symptoms can be vague and there may be no obvious external signs of a problem.
The symptoms of an internal abscess can also vary depending on exactly where in the body the abscess develops. For example, a liver abscess may cause jaundice (yellowing of the skin and the whites of the eyes), whereas an abscess in or near the lungs may cause a coughor shortness of breath.
General symptoms of an internal abscess can include:
discomfort in the area of the abscess
pain or swelling in your tummy (abdomen)
loss of appetite and weight loss
extreme tiredness (fatigue)
diarrhoea or constipation
Causes of an abscess
Most abscesses are caused by a bacterial infection. However, they can very occasionally develop due to an infection by viruses, fungi or parasites.
When foreign organisms such as bacteria enter the body, the immune system sends white blood cells to fight the infection. This causes swelling (inflammation) at the site of infection and the death of nearby tissue, creating a hole called a cavity, which fills with pus to form an abscess.
The pus contains a mixture of dead tissue, white blood cells and bacteria. The abscess may get larger and more painful as the infection continues and more pus is produced.
Most abscesses occur as a result of staphylococcal bacteria andstreptococcal bacteria.
Some types of staphylococcal bacteria produce a toxin called Panton-Valentine leukocidin (PVL), which kills white blood cells. This causes the body to make more cells to keep fighting the infection, and can lead to repeated skin infections.
When bacteria gets under the surface of your skin, an abscess can form. This can occur anywhere on the body, although skin abscesses tend to be more common in the:
hands and feet
Bacteria can get into your skin and cause an abscess if you have a minor skin wound, such as a small cut or graze, or if a sebaceous gland (oil gland) or sweat gland in your skin becomes blocked.
Abscesses that develop inside the tummy (abdomen) are caused by an infection reaching tissue deeper within the body. This can occur as a result of:
an infection spreading from a nearby area
There are many ways an infection can spread into the abdomen and cause an abscess to develop.
For example, a lung abscess can occur due to a bacterial infection in your lungs, such as pneumonia, and a burst appendix can spread bacteria within your abdomen.
In addition to the specific causes mentioned above, things that increase the likelihood of an abscess developing can include:
having a weakened immune system – this could be due to a medical condition such as HIV, or a treatment such as chemotherapy
having an underlying inflammatory condition, such as hidradenitis suppurativa, panniculitis, acute pancreatitis and inflammatory bowel disease (IBD)
being a carrier of staphylococcal bacteria
However, many abscesses develop in people who are otherwise generally healthy.
Diagnosing an abscess
See your GP if you think you may have an abscess. There are several tests used to diagnose an abscess, depending on where it's located.
If you have a skin abscess, your GP will examine the affected area, ask how long you've had the abscess, whether you've injured that area and whether you have any other symptoms.
A sample of pus may be taken from your abscess and sent for testing. This allows the specific bacteria causing the abscess to be identified, which can help determine the best way of treating it.
If you've had more than one skin abscess, you may be asked to give a urine sample. This will be tested for glucose, which is a sign ofdiabetes. People with diabetes have an increased risk of developing skin abscesses.
If you have recurring boils and abscesses, your GP may ask the laboratory to test the bacteria further to see if it is producing Panton-Valentine leukocidin (PVL) toxin. Additional treatments may then be recommended, such as a body wash or an antibiotic cream, to stop these bacteria living on the body.
Abscesses that develop inside your body are more difficult to diagnose than skin abscesses because they cannot be seen. Your GP will ask you about your symptoms and any other health conditions you may have.
If your GP suspects a problem such as an internal abscess, they may refer you for a scan to identify the problem. For example, you may have:
a computerised tomography (CT) scan – where a series of X-rays are taken to produce an image of the inside of your body
a magnetic resonance imaging (MRI) scan – where magnetic fields and radio waves are used to produce an image of the inside of your body
an ultrasound scan – where high-frequency sound waves are used to produce an image of the inside of your body
an X-ray – where high-energy radiation is used to produce an image of the inside of your body
These scans will help determine the size of the abscess and where it is in your body.
Treating an abscess
Abscesses can be treated in a number of different ways, depending on the type of abscess and how large it is.
The main treatment options include:
a drainage procedure
Some small skin abscesses may drain naturally and get better without the need for treatment. Applying heat in the form of a warm compress, such as a warm flannel, may help reduce any swelling and speed up healing.
However, the flannel should be thoroughly washed afterwards and not used by other people, to avoid spreading the infection.
For larger or persistent skin abscesses, your GP may prescribe a course of antibiotics to help clear the infection and prevent it from spreading.
A course of antibiotics will usually start before a specific type of bacteria has been identified, so "broad-spectrum" antibiotics will initially be given. These are designed to work against a wide range of known infectious bacteria and will usually cure most common infections. Once a specific bacterium has been identified from a pus sample, a more "focused" antibiotic can be used.
Sometimes, especially with recurrent infections, you may need to wash off all the bacteria from your body to prevent re-infection (decolonisation). This can be done using antiseptic soap for most of your body and an antibiotic cream for the inside of your nose.
However, antibiotics alone may not be enough to clear a skin abscess, and the pus will need to be drained to clear the infection. If a skin abscess is not drained, it may continue to grow and fill with pus until it bursts, which can be very painful and can cause the infection to spread or recur.
Incision and drainage
If your skin abscess needs draining, you will probably have a small operation carried out under anaesthetic – usually a local anaesthetic, where you remain awake and the area around the abscess is numbed.
During the procedure, the surgeon will make a cut (incision) in the abscess, to allow the pus to drain out. They may also take a sample of pus for testing.
Once all of the pus has been removed, the surgeon will clean the hole that is left by the abscess using sterile saline (a salt solution).
The abscess will be left open but covered with a wound dressing, so if any more pus is produced it can drain away easily. If the abscess is deep, an antiseptic dressing (gauze wick) may be placed inside the wound to keep it open.
The procedure may leave a small scar.
The pus will usually need to be drained from an internal abscess, either by using a needle inserted through the skin (percutaneous abscess drainage) or with surgery.
The method used will depend on the size of your abscess and where it is in your body. Antibiotics will usually be given at the same time, to help kill the infection and prevent it spreading. These may be given as tablets or directly into a vein (intravenously).
As with skin abscesses, broad-spectrum antibiotics will initially be given until a specific bacteria has been identified from a pus sample.
If the internal abscess is small, your surgeon may be able to drain it using a fine needle. Depending on the location of the abscess, this may be carried out using either a local or general anaesthetic.
The surgeon may use ultrasound scans or computerised tomography (CT) scans to help guide the needle into the right place.
Once the abscess has been located, the surgeon will drain the pus using the needle. They may make a small incision in your skin over the abscess, then insert a thin plastic tube called a drainage catheter into it.
The catheter will allow the pus to drain out into a bag, and may have to be left in place for up to a week.
This procedure may be carried out as a day case procedure, which means you will be able to go home the same day, although some people will need to stay in hospital for a few days.
As with the incision and drainage procedure for skin abscesses, percutaneous drainage may leave a small scar.
If your internal abscess is too large to be drained with a needle, if a needle cannot get to the abscess safely, or if needle drainage has not been effective in removing all of the pus, you may need to undergo surgery.
The type of surgery you have will depend on the type of internal abscess you have and where it is in your body, but it will generally involve making a larger incision in your skin to allow the pus to be washed out.
Preventing an abscess
It's difficult to prevent internal abscesses, as they are often complications of other conditions, but you may be able to reduce your risk of skin abscesses with skin care and a healthy lifestyle.
Look after your skin
Ensuring that your skin is clean, healthy and largely free of bacteria can help reduce the risk of skin abscesses developing.
You can reduce the risk of spreading bacteria by:
washing your hands regularly
encouraging people in your family to wash their hands regularly
using separate towels and not sharing baths
waiting until your skin abscess is fully treated and healed before using any communal equipment, such as gym equipment, saunas or swimming pools
Do not squeeze the pus out of the abscess yourself, because this can easily spread the bacteria to other areas of your skin. If you use tissues to wipe any pus away from your abscess, dispose of them straight away to avoid germs spreading. Wash your hands after you have disposed of the tissues.
Take care when shaving your face, legs, underarm areas or bikini area to avoid nicking your skin. Clean any wounds immediately and visit your GP or local walk-in centre if you think there may be something trapped in your skin. Do not share razors or toothbrushes
Eating a diet that is rich in vitamins and minerals can help your immune system work properly and fight off infection. You should aim to eat at least five portions of fruit and vegetables a day.
Maintain a healthy weight
If you are overweight, you may have a greater risk of developing skin abscesses.
This can occur as a result of bacteria found naturally on your body becoming trapped in the folds of your skin. People who are overweight or obese are also at greater risk of developing diabetes, which increases the likelihood of skin abscesses developing.
Smoking causes a wide range of serious health problems that can affect your immune system’s ability to fight infection. If you smoke, giving up is one of the best things you can do to improve your general health.
Your GP can give you help, advice and support about giving up smoking. You can also find more information and advice on the Smokefree website.