A skin boil is a bacterial infection of a hair follicle, according to WebMD. Boils most often appear on the face, armpits, shoulders, neck and buttocks. Symptoms are a painful, red bump in the skin that starts out hard, and then softens, grows and becomes even more painful.
Eventually, an area of pus appears on top of the boil, explains WebMD. A boil on the eyelid is known as a sty. Boils also come in clusters. When they do, the cluster is called a carbuncle. The infection that gives rise to a boil can worsen if it is not treated. In that case, the skin around the boil becomes inflamed, painful and swollen, and more boils erupt around the first one. The person might also become feverish, suffer from chills and develop swollen lymph nodes. These symptoms are reasons to seek medical help.
A patient should also see a doctor if red streaks appear around the boil and the pain becomes intolerable, notes WebMD. A doctor should also be sought if the boil does not drain. People with compromised immune systems or those who suffer from diabetes, a heart murmur or are generally in bad health should also seek medical help if they develop a boil.