A furuncle (boil) is a skin infection involving an entire hair follicle and nearby skin tissue.

See also: Carbunculosis

Furuncles are very common. Furuncles are generally caused by Staphylococcus aureus, but they may be caused by other bacteria or fungi found on the skin's surface. Damage to the hair follicle allows these bacteria to enter deeper into the tissues of the follicle and the subcutaneous tissue.

Furuncles may occur in the hair follicles anywhere on the body, but they are most common on the face, neck, armpit, buttocks, and thighs. Furuncles can be single or multiple.

A furuncle may begin as a tender, pinkish-red, swollen nodule but ultimately feel like a water-filled balloon. Pain gets worse as it fills with pus and dead tissue. Pain improves as it drains. It may drain on its own. More often the patient or someone else opens the furuncle.

The furuncle:

• Is usually pea-sized, but may be as large as a golf ball
• May develop white or yellow centers (pustules)
• May join with another furuncle or spread to other skin areas
• May grow rapidly
• May weep, ooze, crust

Other symptoms may include:

• Fatigue
• Fever
• General ill-feeling
• Itching before furuncle develops
• Skin redness or inflammation around the lesion

Diagnosis is primarily based on the appearance of the skin. Skin or mucosal biopsy culture may show staphylococcus or other bacteria.

Furuncles may heal on their own after an initial period of itching and mild pain. More often, they increase in discomfort as pus collects. They finally burst, drain, and then heal on their own.

Furuncles usually must drain before they will heal. This most often occurs in less than 2 weeks. Treatment by a health care provider is needed if a furncle lasts longer than 2 weeks, returns, is located on the spine or the middle of the face, or occurs with a fever or other symptoms because the infection may spread and cause complications.

Warm moist compresses encourage furuncles to drain, which speeds healing. Gently soak the area with a warm, moist cloth several times each day. Deep or large lesions may need to be drained surgically by a health care provider. Never squeeze a boil or attempt to cut it open it at home because this can spread the infection and make it worse.

Meticulous hygiene is important to prevent the spread of infection. Draining lesions should be cleaned frequently. You should wash your hands very well The after touching a furuncle. Do not re-use or share washcloths or towels. Clothing, washcloths, towels, and sheets or other items that contact infected areas should be washed in very hot (preferably boiling) water. Dressings should be changed frequently and discarded in a manner that contains the drainage, such as by placing them in a bag that can be closed tightly before discarding.

Antibacterial soaps and topical antibiotics are of little benefit once a furuncle has formed. Systemic antibiotics may help to control infection in those with repeated furuncles.

Some people have recurrent bouts with abscesses and little success at preventing them. Furuncles can be very painful if they occur in areas like the ear canal or nose. A health care provider should treat furuncles of the nose. Furuncles that develop close together may expand and join, causing a condition called carbunculosis.

• Abscess of the skin, spinal cord, brain, kidneys, or other organ
• Brain infection
• Endocarditis
• Osteomyelitis
• Permanent scarring
• Sepsis
• Spinal cord infection
• Spread of infection to other parts of the body or skin surfaces

Call for an appointment with your health care provider if furuncles:

• Appear on the face or spine
• Continue to occur
• Do not heal with home treatment within 1 week
• Occur along with a fever, red streaks extending out from the sore, large fluid collections around the boil, or other symptoms

The following may help prevent the spread of infection:

• Antibacterial soaps
• Antiseptic (germ-killing) washes
• Good hygiene (such as thorough handwashing)