Furuncle (Boil)

Key Points
Skin infection involving an entire hair follicle and the surrounding tissue
Usually caused by Staphylococcus aureus, but can be caused by other bacteria
Often begins as a tender papule with a pinkish hue, progressing to a pea-sized or larger nodule, which may develop a white or yellow pus filled center

Furuncles, more commonly known as boils, are infections of the hair follicle caused by bacteria on the skin's surface. Furuncles will often heal on their own after a short period, but cause discomfort and pain as they fill with pus and dead tissue, and may need to be drained to begin the healing process.

Furuncles often form when staphylococcus aureus grows down into the hair follicle , infecting the follicle. While most common in teenagers and young adults, people such as athletes involved in contact sports with shared equipment, persons with lowered immune systems, and those with other pre-existing skin conditions, such as eczema, that impair normal skin function are more vulnerable to developing furuncles.

Differential Diagnosis (Other conditions with similar appearance)
Carbuncle (the coalescence of multiple furuncles)
Epidermal inclusion Cyst (sebaceous Cyst)
Acne vulgaris (Acne Cyst)

Diagnosis
Key Points
Diagnosis based on skin appearance
Culture, if performed, may identify staphylococcus or other bacteria

Furuncles are almost always diagnosed based on the appearance of the skin. The affected area will be a red-to-purple in color, tender lump on an area of the skin that also has hair (i.e. almost anywhere except the palms or soles). The lump eventually becomes filled with visible pus at its center (yellow or white in color) that you will be able to see. The pus is a mixture of bacteria and white blood cells, which fight infection. Common areas for furuncles to form include the buttocks, armpits, groin, neck, shoulders, face, or any area of the skin which is sweaty and/or exposed to frequent friction.

Treatment
Will often heal on their own, after bursting and draining
Application of warm wet compresses several times a day will encourage drainage
Hygiene of the area is important, including washing the area thoroughly with soap and water and keeping a clean dressing on the furuncle
Especially deep or large examples, or furuncles lasting longer than two weeks, should be treated by a health care professional, in addition to any furuncle on the the face, or one accompanied by fever. Incision and drainage is very important to speed resolution of a furuncle
Systemic antibiotics may be prescribed for those patients who experience repetitive furuncles to control infection

Unless a furuncle is particularly large, part of a grouping, or in an area such as the face where it may present risk of spreading the infection, they are easily treated. It is important to note that a furuncle will only begin healing after it has been drained of the pus and fluid at its center. This process can be encouraged by the application of a warm wet compress to the area several times per day, but will sometimes occur on its own. Antibacterial soaps and topical Antibiotics provide very little benefit once a furuncle has formed, so their usefulness as a treatment option is limited.

Meticulous hygiene is critical in assisting the healing process and preventing further infection. Furuncles in the process of draining should be cleaned frequently, as well as washing hands thoroughly after touching the affected area. Affected persons should not reuse or share washcloths or towels, and should wash all articles which come in contact with the area in very hot water.