Most abscesses are caused by a bacterial infection.
Your immune system fights the bacteria with white blood cells. When this happens, some nearby tissue dies. This creates a hole 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.
Some types of staphylococcal bacteria produce a toxin called Panton-Valentine leukocidin (PVL). This kills white blood cells. It causes the body to make more cells to keep fighting the infection. It can lead to repeated skin infections.
In rare cases, a virus, fungi or parasites may cause an abscess.
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. For example, a small cut or graze, or if a sebaceous gland (oil gland) or sweat gland in your skin becomes blocked.
Abscesses inside the tummy (abdomen) are caused by an infection in tissue deeper in the body.
This can happen as a result of:
- an injury
- abdominal surgery
- an infection spreading from a nearby area
There are many ways an infection can spread into the tummy and cause an abscess to develop.
For example, a lung abscess can form after a bacterial infection in your lungs, such as pneumonia. A burst appendix can spread bacteria within your tummy.
Other things that increase the chance of an abscess developing include:
- a weak immune system - can be caused by a medical condition such as HIV or a treatment such as chemotherapy
- having diabetes
- having an underlying inflammatory condition, such as hidradenitis suppurativa
- being a carrier of staphylococcal bacteria
Many abscesses develop in people who are otherwise generally healthy.