BOIL, in medicine, a progressive local inflammation of the skin, taking the form of a hard suppurating mass with a core of dead tissue, resulting from infection by a microbe, Staphy lococcus pyogenes, and commonly occurring in young persons, or as a complication in certain diseases. Usually an infected hair follicle is the starting point. Treatment is local and systemic, the latter being necessary since boils are apt to occur in persons who are "run down." In the English Bible, and also in popular medical terminology, "boil" is used of various forms of ulcerous affection. The boils which were one of the plagues in Egypt were apparently the bubonic plague. The terms Aleppo boil (or button), Delhi boil, Oriental boil, Biskra button, etc., have been given to a tropical epidemic characterized by ulcers on the face, due to a micro-organism (Leishmania).