What is an abscess? An abscess is a collection of pus inside your body. Abscesses usually form because of an infection or because a foreign object becomes trapped in your body. When your body fights an infection or tries to destroy a foreign object trapped inside, white blood cells fill the affected tissues, and the resulting fluid is called pus. Pus contains living and dead bacteria, living and dead white blood cells, and the remnants of the cells and tissue that were killed or injured by the infection or by your body’s immune response. Abscesses often form in or near the skin or in the mouth near the teeth. An abscess often looks like a bump of any size that is red and often swollen, and inside of the bump is a pus-filled space. It is unwise to attempt to drain any abscess—no matter how superficial. Doing so could lead to a lethal blood-borne infection (sepsis). Abscesses are usually treatable with antibiotics, surgery, or a combination of these. In many cases, surgical drainage of an abscess is required. A specimen of the fluid within the abscess is generally sent to the laboratory to identify any causative bacteria. Most abscesses can be treated effectively and have fairly few complications, though some abscesses can occur deeper in your body or in your organs and can cause much more serious damage. Seek prompt medical care if you suspect you have an abscess, or if you are being treated for an abscess and the condition persists or causes you concern.