A boil (or furuncle) is a skin infection that is usually caused by the bacteria Staphylococcus aureus (staph). Other bacteria or fungi can also cause boils.
A boil forms a lump that goes deep into the skin. It may have a central “head” filled with pus. Boils usually occur on the face, neck, armpits, buttocks, and thighs, but can appear anywhere on the body. They can be painful.
In most boils, the bacteria also infect hair follicles, the sacs that contain the roots of hair and oil glands. An infection of the hair follicles is called folliculitis. A boil can also develop from a cut in the skin.
A carbuncle is a group of boils located in one area of the body. Carbuncles may have more than one head that fills with pus. Some people can get boils or carbuncles over and over in one spot of the body.
People with certain illnesses like diabetes are more likely to get boils. Another risk factor is having another skin condition such as eczema, or conditions that reduce the skin’s ability to fight germs.
This skin infection can be spread to other people. On rare occasions, it can be serious, and cause infection of the bloodstream, infection of other body parts, or general infection of the body (sepsis). A serious infection with MRSA (methicillin-resistant Staphylococcus aureus) can also occur.
A boil may start out as a sore, raised area that is pinkish red in color. Over time, the boil may fill with clear liquid or pus, and grow in size.
Symptoms of a boil include the following:
Carbuncles cause a deeper and more serious infection than boils, so their symptoms may be more severe. In addition to the same symptoms as seen in boils, carbuncles may also:
A boil or carbuncle should never be squeezed or pricked with a pin or sharp object to release the pus and fluid. This can spread the infection to other parts of the skin.
If left alone, a boil will break and drain on its own over time. In certain cases, a doctor may need to cut into the skin to drain the pus. Once the fluid and pus drains from the boil or carbuncle, it will heal. The doctor may also prescribe antibiotics if there is a serious infection.
If you have a boil, you can do the following:
A boil or carbuncle can happen despite the best hygiene. However, you can prevent boils if you:
If you have a carbuncle:
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 04/15/2016