Boil and Carbuncle 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. A boil looks
like a red, swollen, painful bump under the skin. As the
infection gets worse, a whitish tip, also cal