An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends beyond the swelling. Carbuncles and boils are types of abscess that often involve hair follicles, with carbuncles being larger.
They are usually caused by a bacterial infection. Often many different types of bacteria are involved in a single infection. In the United States and many other areas of the world the most common bacteria present is methicillin-resistant Staphylococcus aureus. Rarely, parasites can cause abscesses; this is more common in the developing world. Diagnosis of a skin abscess is usually made based on what it looks like and is confirmed by cutting it open. Ultrasound imaging may be useful in cases in which the diagnosis is not clear. In abscesses around the anus, computer tomography (CT) may be important to look for deeper infection.
Standard treatment for most skin or soft tissue abscesses is cutting it open and drainage. There does not appear to be any benefit from also using antibiotics for this type of abscess in most people who are otherwise healthy. A small amount of evidence supports not packing the cavity that remains with gauze after drainage. Closing this cavity right after draining it rather than leaving it open may speed healing without increasing the risk of the abscess returning. Sucking out the pus with a needle is often not sufficient.
Skin abscesses are common and have become more common in recent years. Risk factors include intravenous drug use with rates reported as high as 65% in this population. In 2005 in the United States, 3.2 million people went to the emergency department for an abscess. In Australia, around 13,000 people were hospitalized in 2008 with the condition.