A small abscess (collection of pus) of the skin. A group of nearby boils can come together to form one large boil (a carbuncle). The infection arises from hair follicles and rapidly turns into an abscess. The most common bacteria is Staphylococcus aureus with MRSA (methicillin resistant Staphylococcus aureus) becoming more common. Boils can occur anywhere on the body but are more commonly found on the back, neck or in skin areas that are shaved frequently. The infection can be contagious and is more common in those people with diabetes or other disorders that depress the immune system.