Abscesses

Summary

• An abscess is an accumulation of pus
• It can occur anywhere in the body
• Abscesses are commonly found in the following sites: face, neck, groin, arm pits, legs, scalp and mouth
• Abscesses often heal on their own. Otherwise, they can be treated by antibiotics, surgical drainage, or both

Alternative names

A ‘furuncle’ is a small, single abscess near the skin’s surface.

A ‘carbuncle’ is a large abscess.

‘Empyema’ describes the accumulation of pus within a space or cavity.

What is an abscess?

An abscess is an accumulation of pus, usually caused by a bacterial infection.

What causes an abscess?

A bacterial infection may lead to an abscess in several ways. For example, using a contaminated needle can introduce bacteria under the skin. Or bacteria may spread from an infection elsewhere in the body. Even bacteria that normally live on the body, but cause no harm, can sometimes cause an abscess. Secondary infection may occur around a surgical stitch inserted to close an operation wound.

When bacteria invade healthy tissue, the infection spreads through the area. Some cells die and disintegrate, leaving spaces where fluid and infected cells gather. White blood cells, which protect the body from infection, move into these spaces. After surrounding the bacteria, the white blood cells die, forming pus. As pus collects, it pushes healthy tissue aside. Walls of tissue eventually grow around the abscess to prevent the infection spreading. If an abscess ruptures (bursts) internally, the infection may spread inside the body or under the skin surface.

Abscesses can develop anywhere in the body, including the, mouth, bone, rectum and muscle tissue, and in organs such as the liver, lungs or even the brain. They are fairly common in or just below the skin, especially on the face.

The most common cause of pyogenic abscess formation is related to poor body hygiene, infrequent washing of hands, crowding, poverty, hot weather and friction of body parts (i.e. in the groin).

Who gets abscesses and who is at risk?

Anyone can get abscesses. Diabetics, elderly people and those whose immune systems are not functioning well are particularly vulnerable.

Symptoms and signs of an abscess

Symptoms of an abscess can include pain, warmth, tenderness, swelling, redness and fever. An abscess that forms just under the skin usually creates a visible bump. When an abscess is about to rupture, and the overlying skin thins, it develops a white centre. However, the symptoms of an abscess depend on its location, and whether it affects the function of an organ or a nerve.

How are abscesses diagnosed?

Although doctors are able to spot an abscess on or just beneath the skin, a deep abscess is harder to detect. In this case, a blood test might be necessary, often revealing an abnormally large number of white blood cells. X-rays, ultrasound scanning, or magnetic resonance imaging (MRI) can be used to establish the size and position of an abscess. To distinguish an abscess from a tumour, doctors sometimes need to obtain a sample of the pus or surgically remove the abscess.

Can abscesses be prevented?

The incidence of abscess formation can be drastically reduced by increasing personal hygiene and washing of the hands. Regular showering or bathing is needed to remove sweat and local bacteria.

Tooth abscesses can be prevented with regular dental care. This includes daily brushing with fluoride toothpaste, flossing, and regular dental check-ups. Plaque build-up and dental caries is thereby prevented.

The use of sterile, disposable, hypodermic needles is also important.

How is an abscess treated?

Often, an abscess will heal by spontaneous rupturing (bursting). Sometimes, if the body can destroy the infection and absorb the contents, the abscess will slowly disappear without rupturing.

To hasten this process, a doctor can pierce and drain the abscess. This often needs to be performed under general anaesthesia. Because large abscesses can leave a large empty space when they are drained, your doctor might temporarily pack this space with gauze. Sometimes, it is necessary to insert artificial drains (thin plastic tubes) for a few days.

Your doctor might prescribe antibiotics to prevent a recurrence, or to eradicate an infection that the abscess has caused to spread to other parts of the body. In most cases, orally administered antibiotics are effective in resolving the local induration and inflammation, as well as preventing satellite abscess formation. Healing is speeded up by surgical drainage or lancing the abscess. Intravenous antibiotics are needed if the person is very sick and toxic. Topical antibiotics are not advised, as this practice can lead to skin sensitivity and allergic reactions.

A tooth abscess is usually treated by means of a root canal procedure and oral antibiotics.

What is the outcome of an abscess?

The outcome depends on the location of the abscess. Usually, an abscess near the surface of the skin should heal quickly once it has ruptured. It might leave behind a small, hard lump under the skin.

When to call the doctor

Any unexplained lump, especially when accompanied by fever and pain, should be discussed with a doctor. Also see your doctor if you have an abscess that does not heal on its own or continues to throb. Call the dentist if you have continual, throbbing pain in your gums.

(Reviewed by Prof Don du Toit)