A furuncule, or boil, is an acute, deep-seated, circumscribed inflammation about a skin gland or hair follicle, causing a round, red and very painful, firm elevation of the skin that usually undergoes purulent softening and expels a necrotic plug or core. Often it starts as a small hardness in the skin or subcutaneous tissue and increases in several days to a bright or bluish red bean- to cherry-sized note upon the apex of which the skin gradually becomes thin and discloses yellow pus beneath. The central point ruptures, the opening enlarges and more or less thick pus escapes, sometimes tinged with blood. At the same time or within a couple of days a tenacious, pulpy mass of necrotic fibrous tissue is expelled. The cavity then heals and leaves a violet scar that in time fades to white.