Boil (or furuncle) is a skin disease caused by the infection of hair follicles, resulting in the localized accumulation of pus and dead tissue. Individual boils can cluster together and form an interconnected network of boils called carbuncles.
Boils are red, pus-filled lumps that are tender, warm, and extremely painful. A yellow or white point at the center of the lump can be seen when the boil is ready to drain or discharge pus. An abscess is also a contained collection of pus; however, it can occur anywhere in or on the body. A boil always involves a hair follicle.
In a severe infection, multiple boils may develop and the patient may experience fever and swollen lymph nodes. A recurring boil is called chronic furunculosis. Risk factors for furunculosis include bacterial carriage in the nostrils, diabetes mellitus, obesity, lymphoproliferative neoplasms, malnutrition, and use of immunosuppressive drugs.
In some people, itching may develop before the lumps begin to form. Boils are most often found on the back, stomach, underarms, shoulders, face, lip, eyes, nose, thighs and buttocks, but may also be found elsewhere.
Sometimes boils will exude an unpleasant smell, particularly when drained or when discharge is present, due to the presence of bacteria in the discharge.
Usually, the cause is bacteria such as staphylococci. Bacterial colonization begins in the hair follicles and can lead to local cellulitis and abscess formation.
Applying warm compresses to a boil can help it to drain. Large boils should be incised and drained. Antibiotic therapy is advisable for large or recurrent boils or those that occur in sensitive areas (such as around or in the nostrils or in the ear).