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Abscess

Overview

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An abscess is a painful collection of pus that is caused by a bacterial infection. Abscesses can be divided into two types:

  • those that develop just under the skin, and
  • those that develop inside the body.

What does an abscess look and feel like?

A skin abscess often appears as a swollen, pus-filled lump under the surface of the skin, or it may look more like an open break in the skin. Abscesses are often red and painful. A boil is a common example of a skin abscess.

Abscesses inside the body are not usually visible, making them more difficult to identify. They can develop within an organ, such as in the lungs, or brain, or in the spaces between organs, causing pain in the affected area.

Who is affected by 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 among people who have diabetes.

Internal abscesses often develop as a complication of an existing condition, such as an abscess in the tonsils after a bout of tonsillitis (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.

How is an abscess treated?

Abscesses can be treated with antibiotics to clear the infection, and surgery to drain away the pus. Without treatment, an abscess will usually continue to become larger and more painful until it bursts, which can cause several complications.

Causes

Most abscesses are caused by a bacterial infection. The way that bacteria gets into your body to cause an abscess differs between skin abscesses and internal abscesses.

How bacteria cause an abscess

When a type of bacteria is able to enter your body, your immune system tries to fight it off by sending white blood cells to the affected area. As your white blood cells attack the bacteria, some of the tissue at the site of the infection dies, causing a hollow to form.

The hollow 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.

Some types of bacteria, such as Staphylococcus aureus, are more likely to result in large amounts of pus than others. This is because it produces toxins that damage your body’s tissue and break it down, creating pus.

See the ‘useful links’ section for more information about Staphylococcal infections.

Causes of skin abscesses

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

Boils are the most common type of skin abscess, and occur when bacteria enters the root of a hair on your skin. 

In most cases, skin abscesses occur on their own, and are not a sign of an underlying health problem.

However, you are more likely to develop a skin abscess if you have diabetes. This is because diabetes can cause damage to your nerves, which can mean that you do not feel any minor cuts and grazes to your skin. Bacteria can then enter your skin and cause an abscess.

Causes of internal abscesses

An abscess can occur inside your body when bacteria spread from an existing infection. A lung abscess can be caused by a bacterial infection that is already present in your lungs, such as pneumonia (inflammation of the tissues of your lungs).

Bacteria can also spread from other areas of your body through your bloodstream. For example, pneumonia can cause an abscess in your brain if bacteria gets into your blood and reaches your brain.

However, internal abscesses such as these are usually very rare. They tend to occur in people who have an underlying health problem (such as a brain abscess that develops following a severe head wound). Internal abscess can also sometimes develop in people with damaged immune systems, such as those with HIV, or those who are having chemotherapy treatment for cancer

Diagnosis

You should see your GP if you think that you may have an abscess. How an abscess is diagnosed will depend on where it is located.

Diagnosing skin abscesses

If you have a skin abscess, your GP will examine the affected area. They may also ask you how long the abscess has been there, if you have been injured in that area, and whether you have any other symptoms.

If you have had more than one skin abscess, your GP may also ask you for a urine sample. This will be tested to see if you have glucose (sugar) in your urine, which is a sign of diabetes. This is because skin abscesses are more common among people who have diabetes.

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 about any other health conditions that you may have.

If your GP thinks that you have an internal abscess, to confirm the diagnosis you may need to have an ultrasound scan or an X-ray.

An ultrasound scan uses high frequency sound waves to produce an image of the inside of your body. An X-ray does the same thing using high energy radiation.

Treatment

Abscesses can be treated with antibiotics, and either a drainage procedure, or surgery, to remove the pus.

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

Treating a skin abscess

If you have a skin abscess, it is likely that your GP will prescribe antibiotics to help clear the infection. If your abscess is small, antibiotics may be the only treatment that you need to kill the bacteria so that the abscess can heal.

However, in most cases, antibiotics alone will not be enough to clear a skin abscess. It is usually necessary to drain the pus from a skin abscess in order to clear the infection.

If a skin abscess is not drained, it may continue to become larger 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 come back, or the infection to spread.

Incision and drainage

If you need to have your skin abscess drained, it is likely that you will have a small operation under anaesthetic. The anaesthetic that is used will depend on the size and severity of your skin abscess. You may have a local anaesthetic (you will be awake, but the area of the abscess will be numb), or a general anaestheic (you will be asleep).

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

Your abscess will be left open so that any more pus that is produced can be drained away. If your abscess is deep, you may need to have an antiseptic dressing placed inside it to keep it open. Once the procedure is complete, the wound should heal in approximately 14 days. It may leave a small scar.

Treating an internal abscess

As with a skin abscess, the first type of treatment for an abscess inside your body will be antibiotics to help fight the infection.

You will then need to have an operation to drain your abscess of pus. The way this is done will depend on the size of your abscess, and whereabouts in your body it is.

Incision and drainage

If the internal abscess is small, your surgeon may be able to drain it using a fine needle. Depending on where your abscess is, this may be carried out using either local, or general, anaesthetic.

During a drainage procedure using a needle, an ultrasound scan may be used to help the surgeon guide the needle into the right place.

An ultrasound scan uses high-frequency sound waves to produce an image of the inside of your body, and can show your surgeon exactly where your abscess is.

Once the needle has entered the abscess, the pus will be drawn out into the needle. Your surgeon will then cover the area with a dressing.

However, 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 a different form of surgery.

Your surgeon may make an incision (cut) in your skin over the abscess, and insert a fine plastic tube into the abscess. The tube allows the pus to drain out, and it will be left in place until all the pus has been removed. As with needle drainage, you may be given a local, or a general anaesthetic, for this procedure.

Prevention

As abscesses inside the body tend to occur as a complication of another condition, there is nothing you can do to prevent them. However, the following advice may help you to prevent skin abscesses developing.

Look after your skin

Ensuring that your skin is clean, healthy, and free of bacteria can help to reduce the risk of skin abscesses developing. You should wash your skin at least once a day using water and soap.

You should also take care when shaving your face, legs, underarms, or bikini area, to avoid nicking your skin. Clean any wounds immediately and visit your GP, or local NHS walk-in centre if you think there may be something trapped in your skin.

Eat healthily

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

Lose weight if you are overweight or obese

If you are overweight, or obese, you may be more at risk of developing skin abscesses due to bacteria that is found naturally on your body becoming trapped in the folds of your skin.

You are also at greater risk of developing diabetes, which in turn will increase the likelihood of skin abscesses developing.

Do not smoke

Smoking damages your entire body, and can affect your immune system’s ability to fight infection. If you smoke, giving up is the best thing that you can do for your general health.

See the 'useful links' section for further information and advice about eating healthily, losing weight, and giving up smoking.