A boil is also known as so-called furuncle and it belongs among purulent skin infections. It is usually a complication of folliculitis, which is infectious inflammation of hair follicles.


Furuncle is usually caused by bacteria of the staphylococcus origin. The infection can occur anywhere in the skin where there are hair follicles. Development of furuncle is more common in patients with impaired immunity.


The affected area is reddish, swollen and painful. The sores can have different sizes; sometimes it even reaches the size of a ping-pong ball. The lesion is filled with pus, which can spontaneously empty itself. Boils often heal by forming scars. It is inadvisable to try to squeeze the pus out of the boil as there is danger of local bacterial spread and formation of an abscess or even a local phlegmon (e.g. a furuncle on the head or face can cause purulent meningitis) and-or septic condition. Sometimes several furuncles merge into a larger unit that is called carbuncle.


The diagnosis can be confirmed by physical examination of the patient as the boil is well visible by naked eye. When there are signs of sepsis, it is important to take blood cultures to evaluate the bacterial presence and their sensitivity to antibiotics.


Small furuncles usually heal spontaneously but they must be treated hygienically and with local antibiotics, ointments and other preparations. Larger boils are sometimes treated by a surgeon – they are cut open in local anesthesia and the pus is drained to seep up the healing. Infectious complications (especially sepsis) must be treated in an inpatient department.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources