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Author: A/Prof Amanda Oakley, Dermatologist, Hamilton New Zealand, 2013.
An abscess is a cavity filled withpus(pyodermaorsepsis). It contains white blood cells, dead tissue andbacteria.
Cutaneousabscessesmay occur anywhere on the skin, but are most common under the arms, at the base of the spine (pilonidal disease) or around the genitals (for example, Bartholin abscess) andanus.
An abscess usually presents as a hot, red, swollen and painful lump. It may lead tofever, swollenlymphnodes, and illness including potentially dangeroussepticaemia. Non-bacterialabscesses may be cool, skin coloured and painless.
If not treated, an abscess eventually bursts and drains thick yellow pus.
Although it may become 'walled off' by aninflammatoryreaction, an abscess is not surrounded by a true capsule.
A painful abscess is usually due toacutebacterialinfection. Bacteria penetrate a break in the skin such as a puncture wound, or via ahairfollicle. An abscess may alsodeveloparound a foreign body, such as a splinter. The most common causes of infective abscesses are:
Infective abscesses may affect healthy people, but they are more common in the following circumstances.
A sterile abscess maypersistafter an infection has been cleared, as it contains dead ornecrotictissue and inflammatory cells.
A sterile abscess may occur aftercorticosteroidinjection. This is more likely when the medication has spilt intosubcutaneousfat. A foreign-body or otherhypersensitivityreaction to injected material such as bovinecollagenmay also result in abscess formation.
Certain inflammatory skin diseases may cause tissue destruction and abscess formation, in the absence ofpathogens(infectiousmicrobes). These include:
If the cause of an abscess is unknown, the following tests may be undertaken.
An abscess should be explored to remove foreign bodies, and its contents should be removed. This requires making a surgicalincisionand draining the pus. The cavity is then thoroughly washed out withsaline. It should be left open to allow further pus to drain away. Wicks are sometimes inserted if the abscess is deep, to help it drain.
Antibioticsare often prescribed, chosen according to theorganismcausing the abscess and its sensitivities.
If abscesses are due to staphylococcal infection, the risk ofrecurrencecan be minimised by:
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