Back to Health A to Z. Over time, pus forms inside the boil, making it bigger and more painful. Most boils eventually burst and the pus drains away without leaving a scar. This can take from two days to three weeks to happen. It can sometimes be difficult to tell the difference between a boil and a spot, but boils tend to grow bigger and become more painful.
A boil is a painful, pus-filled bump under your skin — the result of a bacterial infection of one or more hair follicles. A carbuncle is a cluster of boils — painful, pus-filled bumps — that form a connected area of infection under the skin. Boils and carbuncles are painful, pus-filled bumps that form under your skin when bacteria infect and inflame one or more of your hair follicles. Boils furuncles usually start as red, tender lumps.
Small boils can usually be treated on your own at home. Small boils that can be treated at home can take anywhere from a few days to three weeks to heal. If you have a large boil or a group of boils carbunculosis , you should see your doctor for treatment. Only your doctor can drain a large boil or carbuncle safely.