Boils and carbuncles

A boil, also called a furuncle, is a localized bacterial infection under the skin that commonly occurs around hair follicles. A carbuncle is two or more boils that have joined together.


Causes/associated factors
Boils are most often caused by Staphylococcus aureus, a type of bacteria often found on the skin. They usually develop in a hair follicle in an area subject to pressure or moisture, such as the buttocks, nape of the neck, armpits or groin. They're also common on the face. A carbuncle, which is a more extensive infection, occurs more often on the back or nape of the neck. Although most boils and carbuncles develop in people who are otherwise healthy, you may be at a greater risk if you:
have poor hygiene
eat poorly
are an alcoholic
wear clothing that persistently rubs on one area of skin
have a skin condition such as acne or dermatitis (inflammation of the upper layer of skin)
have a weak immune system (as with HIV, the virus that causes AIDS, for example)
have a chronic illness, such as diabetes
are overweight and have skin folds that rub together

Signs/symptoms
As the boil develops, the surrounding skin will be taut, red, swollen and tender to the touch. Boils usually develop heads filled with pus that eventually rupture, but sometimes boils disappear before this happens. The symptoms of a carbuncle are similar, but they involve a larger area of skin and are more likely to cause permanent scarring.

Diagnosis
The doctor will ask questions about your medical history and do a skin exam. Lab tests may be needed as well.

Treatment
Treatment for boils depends on severity, how many you have and how often they develop. If you have a small, simple boil, your doctor may recommend the following self-care measures:
Soak the affected area in warm water. Or, use warm, moist packs up to four times a day or every few hours. Warm, moist heat sometimes promotes pus drainage. In other cases, it causes the pus to regress or disappear. Continue to soak or apply warm, moist packs after the wound begins to drain.

Keep the affected area meticulously clean with soap and warm water.

Treat the affected area gently. Do not pick, pinch or squeeze the sore. This may cause the infection to spread.

Until healing is complete, avoid contact sports and activity that may cause sweating or friction in the affected area.
Depending on the boil's size and response to the warm soaks, the doctor may drain it and pack the affected area with sterile gauze. In some cases, oral antibiotics are prescribed.

Carbuncles require prompt medical evaluation and treatment to prevent more serious infections.

If you have recurring boils or carbuncles, your doctor may prescribe antibiotic cream, ointment or pills to be used for a period of months.


Complications
Boils and carbuncles typically respond well to medical treatment, but recurrences and scarring are possible. In some cases, the infection may spread to surrounding tissues or the blood and cause fever and a general feeling of illness.
Rarely, the bacteria from a carbuncle may spread and cause:

endocarditis (inflammation of the membrane that lines the heart)
osteomyelitis (a painful inflammation of bone or bone marrow caused by a bacterial infection)
a brain abscess (a collection of pus inside the brain)
bloodstream infections such as staph-scalded skin syndrome or staph toxic shock syndrome
Rare, but serious, complications can occur as a result of a carbuncle on the face, particularly on the central part of the upper lip or near the nose or forehead. Spread from this type of infection can potentially lead to meningitis (inflammation of the lining of the brain and spinal cord) or a blood clot of the intracranial venous sinus, a condition that can cause stroke-like symptoms. These conditions can be life-threatening if not treated aggressively. Remember, never squeeze a sore to drain it, especially on the central part of the face.


Prevention
To prevent boils and carbuncles, avoid tight-fitting clothing and friction to the skin. Wash your skin regularly with water and a mild soap. If you have a chronic illness, follow your doctor's advice for skin care.
If you have a boil or carbuncle, don't share towels, washcloths or clothing. If recurrences are a problem, your doctor may examine family members and anyone with whom you have intimate contact to determine if there's a staphylococcal "carrier" who may require treatment.