Boils are caused by bacteria, which gain entry to your skin at the root of a hair. Each of the tiny hairs in your skin emerges from a deep pit – the hair follicle. The bacteria multiply at the bottom of the hair follicle and then spread into the nearby skin. The result is a lump that is red and tender, and which may discharge pus before it heals. Often it leaves a scar.
This section offers information on armpit boils as well as general information on boils.