Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Boils and Carbuncles

What Is It?

Boils and carbuncles are skin infections usually caused by Staphylococcus aureus bacteria (staph). These staph infections form pockets in the skin that are filled with pus, a fluid that includes bacteria, dead skin cells and infection-fighting white blood cells. Whether the pocket of pus is called a boil or a carbuncle depends on its location and size:

• A boil, also called a furuncle, begins as a painful infection of a single hair follicle. Boils can grow to be larger than a golf ball, and they commonly occur on the buttocks, face, neck, armpits and groin.

• A carbuncle is a deeper skin infection that involves a group of infected hair follicles in one skin location. Carbuncles often are found on the back of the neck, shoulders, hips and thighs, and they are especially common in middle-aged or elderly men. People with diabetes are more likely to develop carbuncles.