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.
Our skin is covered with a motley collection of bacteria, many of which are capable of causing boils if they can break through the body's immune system. The worst culprit is a bacteria called Staphylococcus aureus, which may be carried quite harmlessly in the nose, throat or on the skin. Boils are not linked to poor personal hygiene, and it can be hard to find a good reason why any particular boil has formed. But some people are more vulnerable. In diabetes mellitus , resistance to bacterial infections is reduced, and skin infections often occur.