Boils and carbuncles are red, painful lumps on the skin that are usually caused by a bacterial infection.
Boils can develop anywhere on your skin, but you’re most likely to get one in an area where there’s a combination of hair, sweat and friction, such as the neck, face or thighs.
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.
Boils and carbuncles are often caused by a type of bacteria called Staphylococcus aureus (staph bacteria) that infects one or more hair follicles. Staph bacteria usually live harmlessly on the surface of the skin or in the lining of the nose.
An active skin boil is contagious