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Abscess

 

An abscess is a painful collection of pus  caused by a bacterial infection. 

This article focuses on two types of abscess:

  • skin abscesses – which can develop anywhere on the body and occur when a bacterial infection causes pus to collect in the skin
  • internal abscesses – which develop inside the body following an infection or an injury

The symptoms of an abscess can vary depending on which type you have.

A skin abscess is often painful and appears as a swollen, pus-filled lump under the surface of the skin, or an open break in the skin.

It's more difficult to identify an abscess inside the body, but signs include pain in the area, a high temperature and generally feeling unwell.

How common are abscesses?

Anyone can develop an abscess, and they can occur almost anywhere in the body.

In most cases, skin abscesses affect people who are otherwise well. They are caused by an infection in the root of a hair or by a blocked sweat gland. Skin abscesses are more common in people with diabetes.

Internal abscesses often develop as a complication of an existing condition, such as an abscess in the tonsils after having acute (severe) tonsillitis. This rare condition is known as quinsy.

People who have an underlying health condition or damage to their immune system are more likely to be affected by internal abscesses.

Outlook

A small skin abscess may drain naturally and disappear without any treatment.

Larger abscesses can be treated with antibiotics to clear the infection and surgery to drain away the pus. Without treatment, an abscess may continue to get larger and more painful until it eventually bursts.

Antibiotics

Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. Examples of antibiotics include amoxicillin, streptomycin and erythromycin.

Immune system

The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Other types of abscess

Dental abscess

A dental abscess is a build-up of pus inside a tooth that is caused by a bacterial infection. Bacteria can infect the tooth as a result of tooth decay.

Dental abscesses can also occur within the bone that supports the tooth structure (alveolar bone) and within the gums. See the Health A-Z topic about Dental abscess for more information.

Brain abscess

Brain abscesses are rare but they can be life threatening. The build-up of pus is caused by bacteria, which can occur following trauma to the skull, after surgery or from a previous infection.

See the Health A-Z topic about Brain abscess for more information.

Bartholin’s abscess

Bartholin’s abscess is a build-up of pus from one of the Bartholin’s glands, which are found on each side of the opening of the vagina. If the gland gets blocked, an abscess can form.

Liver abscess

A liver abscess can be caused by an abdominal infection, such as appendicitis, a blood infection or an infection of the passages that transport bile around the body (the biliary tracts).

Spinal cord abscess

A spinal cord abscess is caused by an infection inside the spine that results in inflammation (swelling) and a build-up of pus around the spinal cord.

Anorectal abscess

An anorectal abscess is a collection of pus that builds up in the rectum and anus. The rectum is the area of the large intestine where stools (faeces) are stored and the anus is the opening through which they are passed.

Anorectal abscesses can be caused by a sexually transmitted infection (STI), a blocked gland or an infection of an anal fissure (a tear or ulcer in the lining of the anal canal). 

Peritonsillar abscess

Peritonsillar abscesses are the most common infections of the head and neck region and usually develop as a result of tonsillitis (an infection of the tonsils).  

The symptoms of an abscess depend on where it develops in your body.

Skin abscesses

Skin abscesses often develop into a swollen, pus-filled lump under the surface of the skin, or they may appear as an open break in the skin. Abscesses are often red and painful.Boils are a common type of skin abscess.

If you have a skin abscess, you may have the following symptoms:

  • a smooth swelling under your skin that can feel hard or firm
  • tenderness in the affected area
  • pain, warmth and redness (erythema) in the affected area
  • an open wound or closed sore
  • pus in the affected area that appears white or yellow or may drain from the affected area
  • a high temperature (fever) of 38C (100.4F) or above
  • chills

Skin abscesses are typically 1-3cm in diameter, although the size can vary. The skin over the abscess may be thin if it is close to tearing.

Internal abscesses

As internal abscesses develop inside the body, they are more difficult to identify than abscesses that appear on the skin. They can develop inside an organ, such as in the lungs or brain, or in the spaces between organs, causing pain in the affected area.

If you have an internal abscess, your symptoms may include:

  • discomfort in the area of the abscess
  • feeling generally unwell
  • a high temperature (fever) of 38C (100.4F) or above
  • pain in your abdomen (tummy)

The symptoms of certain types of deep abscess can also include:

  • weight loss
  • loss of appetite
  • pain and tenderness
  • drowsiness (fatigue)
  • lack of appetite
  • diarrhoea (loose, watery stools)
  • a need to frequently pass urine

Depending on exactly where inside your body the abscess is, you may also have a number of other symptoms.

For example, if you have a dental abscess, you may have toothache, a bitter taste in your mouth and your breath may smell, breast abscess can cause redness, pain and a discharge from your nipple.

Symptoms that could indicate a brain abscess include:

  • headache
  • confusion
  • a high temperature (fever) of 38C (100.4F) or above
Liver
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.

Most abscesses are caused by a bacterial infection.

Bacteria

When bacteria enter your body, your immune system tries to fight the infection by sending white blood cells to the affected area. The white blood cells (polymorphs) kill them and then die. As the white blood cells attack the bacteria, inflammation (swelling) and death of nearby tissue may occur, causing a hollow to form.

The hollow fills with pus to form the 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.

Staphylococcus aureus and streptococci are the most common types of bacteria that cause skin abscesses on the following areas of the body:

  • head and neck
  • limbs
  • underarms
  • torso

See the Health A-Z topic about Staphylococcal infections for more information.

PVL Staphylococcus aureus

Staphylococcus aureus is a type of bacterium found on the surface of healthy skin. It can cause skin infections, such as skin abscesses and boils, and prefers to live in moist areas of the body such as:

  • the armpits
  • the groin
  • inside the nostrils

Some S. aureus bacteria can produce a poisonous substance called Panton-Valentine leukocidin (PVL), which kills the white cells, causing the body to make more white cells to continue to fight the infection.

PVL-positive strains of bacteria are therefore more likely to cause skin infections and abscesses. They can also cause more serious conditions:

  • Septicaemia is blood poisoning caused by bacteria multiplying in the blood. 
  • Pneumonia is swelling (inflammation) of the lungs caused by an infection. Pus collects in the airways and is coughed up as mucus.

Skin abscesses

Bacteria can cause a skin abscess when they get under the surface of your skin. An abscess may occur if you have a minor skin wound, such as a small cut or graze, or if a sebaceous gland (oil gland) or a sweat gland in your skin becomes blocked.

Boils occur as the result of bacteria entering the root of a hair on your skin.

In most cases, skin abscesses are not a sign of an underlying health problem. However, you are more likely to develop a skin abscess if you have diabetes. Diabetes can cause nerve damage, which can mean you are unable to feel any minor cuts and grazes to your skin.

Meticillin-resistant Staphylococcus aureus (MRSA) has been a common cause of skin abscesses in recent years.

Internal abscesses

Abscesses that occur in the abdomen (tummy) can be caused by:

  • an infection
  • a tear (rupture) of the intestine
  • an injury
  • surgery to the abdomen

An abscess can occur inside your body when bacteria spread from an existing infection.

For example, a lung abscess can occur as a result of a bacterial infection that is already present in your lungs, such as pneumonia (inflammation of the lung tissue). Bacteria can also spread from other areas of your body through your bloodstream.

Internal abscesses tend to occur in people who have an underlying health problem, such as a brain abscess that develops after a severe head wound. Internal abscesses can also sometimes develop in people with damaged immune systems, such as those with HIV and AIDSor those who are having chemotherapy treatment for cancer.

Risk factors

Risk factors that are known to increase the likelihood of an abscess developing include:

  • trauma to a specific area of the body
  • a weakened immune system
  • any material getting into the body
  • a drainage system in the body becoming blocked
  • a build-up of fluid in the tissues of the body
  • a haematoma (collection of blood outside a blood vessel)

See your GP if you think you may have an abscess.

Skin abscesses

If you have a skin abscess, your GP will examine the affected area. They may also ask how long you have had the abscess, whether you had an injury in that area and whether you have any other symptoms.

Your GP may decide to take a sample of the pus from your abscess to send it for a gram stain test. This will help determine the type of bacteria causing the abscess. Your GP may also want to send the sample to a laboratory to be grown in a culture so it can be tested against different types of antibiotics.

If you have had more than one skin abscess, your GP may ask you for a urine sample. This will be tested to determine whether you have glucose in your urine, which is a sign of diabetes. People with diabetes have an increased risk of developing skin abscesses.

If you have recurring boils and abscesses, the infection may be caused by Staphylococcus aureus bacteria that produce the Panton-Valentine leukocidin (PVL) toxin (see Abscess - causes).

If your GP thinks this may be causing your skin abscesses, they may ask the laboratory to test the Staphylococcus aureus bacteria to see if it is producing PVL.

Internal abscesses

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 thinks you may have an internal abscess, a number of procedures can be used to confirm the diagnosis. For example, you may have:

  • computerised tomography (CT) scan, where X-rays are taken and a computer is used to produce an image of the inside of your body
  • a magnetic resonance imaging (MRI) scan, where a magnetic field 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, such as a chest X-ray to help diagnose a suspected lung abscess

These techniques will also help determine the size of the abscess and where it is in your body.

Your GP may also want to take a sample of the pus from your abscess so it can be examined under the microscope. This is because the symptoms and images of a tumour can sometimes be similar to an abscess and your GP may want to rule this out before an abscess is diagnosed.

Ruling out other conditions

As well as being used to diagnose internal abscesses, diagnostic techniques such as CT and MRI scans can also be used to rule out a number of other possible conditions:

  • Cysts are small fluid-filled sacs that are usually harmless. There are hundreds of different types of cysts that can affect any part of the body. They can be caused by an infection, a blockage to the flow of fluid in the body and genetic conditions.
  • Tumours are lumps of abnormal tissue that often develop without an obvious cause. Tumours sometimes develop in the brain. See the Health A-Z topic about Brain tumour (low-grade/mixed) for more information
Abscess
An abscess is a lump containing pus, which is made by the body during infection.
Fever
A high temperature, also known as a fever, is when someone's body temperature is 38C (100.4F) or above.
X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.

Abscesses can be treated in a number of different ways including:

  • antibiotics
  • a drainage procedure
  • surgery

The treatment you receive will depend on the type of abscess and how large it is.

Skin abscesses

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 antibiotics to help clear the infection and prevent it from spreading.

Sometimes, you may need to wash off all the bacteria from your body to prevent re-infection, known as decolonisation. The skin is disinfected using additives in the bath or shower and an antibiotic cream is used inside the nose.

In most cases, antibiotics alone will 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.

If an abscess is allowed to burst and drain of pus on its own, there is also a risk that it will not drain properly, causing the abscess to return or the infection to spread.

Incision and drainage

If your skin abscess needs draining, you will probably have a small operation carried out under anaesthetic. The type of anaesthetic used will depend on the size and severity of your skin abscess. However, it is likely you will have a local anaesthetic,where you remain awake and the area around the abscess is numbed.

During the procedure, your surgeon will make a cut in the abscess to allow all of the pus to drain out. They may also take a sample of pus for testing to confirm which bacteria caused the infection. Once all of the pus has been removed, the surgeon will clean the hole that is left by the abscess using a saline (salt) solution.

Your abscess will be left open so that any more pus that is produced can be drained away easily. If your abscess is deep, you may need to have an antiseptic dressing placed inside it to keep it open (gauze wick). The procedure may leave a small scar.

Internal abscesses

The pus must be drained from an internal abscess, either through surgery or by using a needle (percutaneous abscess drainage).

The method used will depend on the size of your abscess and where it is in your body. In most cases, antibiotics are used alongside drainage to help kill the infection and prevent it spreading.

Incision and drainage

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 local or general anaesthetic.

During a drainage procedure using a needle, the surgeon may use ultrasound to help guide the needle into the right place.

Once the abscess has been located, your surgeon will make a cut in your skin over the abscess, before inserting a drainage catheter (a fine, plastic tube) into it. The catheter will allow the pus to drain out into a bag and it will be left in place until all the pus has been removed.

Surgery

If your internal abscess is too large to be drained with a needle, or if needle drainage has not been effective in removing all of the pus, you may need to have surgery to remove the pus.

The type of surgery you have will depend on the type of internal abscess and where it is in your body. You may also need surgery if a needle cannot get to the abscess safely.

Complications

Possible complications of percutaneous abscess drainage include:

  • needing to have surgery if the drainage tube cannot be placed in the abscess successfully during the procedure
  • experiencing a shivering attack while the procedure takes place due to bacteria getting into the bloodstream (this can be treated with antibiotics)

Possible complications of skin abscesses include the spread of infection throughout the bloodstream, leading to more abscesses forming.

Abscess
An abscess is a lump containing pus, which is made by the body during infection.
Anaesthetic
Anaesthetic is a drug used to either numb a part of the body (local) or to put a patient to sleep (general) during surgery.
Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. Examples of antibiotics include amoxicillin and erythromycin.
Catheter
A catheter is a thin, hollow tube usually made of rubber that is placed into the bladder to inject or remove fluid.
Incision
An incision is a cut made in the body with a surgical instrument during an operation.

As abscess that form inside the body often occur as a complication of another condition, there is nothing you can do to prevent them.

The following advice may help prevent skin abscesses.

Skin care

Ensuring that your skin is clean, healthy and 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 if you think there may be something trapped in your skin. Do not share razors or toothbrushes.

Eat healthily

Eating a diet that is rich in vitamins and minerals can help your immune system work properly and fight off infection. Fruit and vegetables are high in vitamins and minerals (aim to eat at least five portions a day).

Weight control

If you are overweight, you are more at 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.

Do not smoke

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 the best thing 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 quit.ie website and in the Health A-Z topic about Quitting smoking.

Abscesses
An abscess is a lump containing pus, which is made by the body during infection.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.