I've got one on my head, which my GP has given me a course of medicine for, but she didn't say why I had got it.
Boils are an infected spot on the skin.
As the pus gathers, pressure inside the boil rises and they become very painful. Boils usually start in an infected hair follicle, as a tiny dimple in the skin, but they can grow to a large size. More extensive boils which spread through the skin and are quite severe are called carbuncles. If boils grow very large, and expand into deeper tissues, they may be called an abscess. Boils usually occur on the skin around the face and neck, the groin and the armpits.