Medically reviewed by Marisa Garshick, MD A carbuncle is a cluster of boils (furuncles) that form under the skin's surface when bacteria infect hair follicles (tiny openings on your skin through which ...

Source: Focus Medica. Red, swollen, painful and pus-filled boils connected to each other under the skin. They often occur on back of the neck, shoulders and thighs. A carbuncle usually develops ...