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

Furuncles are very common. They are caused by staphylococcus bacteria, which are normally found on the skin 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 are generally caused by Staphylococcus aureus, but they may be caused by other bacteria or fungi. They may begin as a tender red subcutaneous nodule but ultimately become fluctuant (feel like a water-filled balloon). A furuncle may drain spontaneously, producing pus. More often the patient or someone else opens the furuncle.

Furuncles can be single or multiple. 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.

The lesions themselves are the primary symptoms:

• Small firm tender red nodule in skin (early)
• Fluctuant nodule (later)
• Located with hair follicles
• Tender, mildly to moderately painful
• May be single or multiple
• Usually pea-sized, but may be as large as a golf ball
• Swollen
• Pink or red
• May grow rapidly
• May develop white or yellow centers (pustules)
• May weep, ooze, crust
• May join together or spread to other skin areas
• Increasing pain as pus and dead tissue fills the area
• Decreasing pain as the area drains
• Skin redness or inflammation around the lesion

Less common symptoms include the following:

• Fever
• Fatigue
• General discomfort, uneasiness, or malaise

Note: Itching (pruritus) of the skin may occur before the lesion develops.

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 progress to pustules that increase in discomfort as pus collects. They finally burst, drain, and then heal spontaneously.

Furuncles usually must drain before they will heal. This most often occurs in less than 2 weeks. Boils that persist longer than 2 weeks, recur, are located on the spine or the middle of the face, or that are accompanied by fever or other symptoms require treatment by a health care provider because of the risk of complications from the spread of infection.

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 the health care provider. Never squeeze a boil or attempt to lance it at home because this can spread the infection and make it worse.

Meticulous hygiene is vital to prevent the spread of infection. Draining lesions should be cleaned frequently. The hands should be washed thoroughly after touching a boil. 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.

Drainage is the definitive treatment.

Full recovery is expected. Some people may experience many repeated episodes.

• Spread of infection to other parts of the body or skin surfaces
• Abscess formation
• Sepsis (general internal infection)
• Abscess of kidneys or other internal organs
• Osteomyelitis
• Endocarditis
• Brain infection
• Brain abscess
• Spinal cord infection
• Spinal cord abscess
• Permanent scarring

Call for an appointment with your health care provider if furuncles (boils) develop and do not heal with home treatment within one week.

Call for an appointment with your health care provider if furuncles recur or are located on the face or spine.

Call for an appointment with your health care provider if boils are accompanied by fever, red streaks extending from the boil, large fluid collections around the boil, or other symptoms.

• Good attention to hygiene
• Antibacterial soaps
• Antiseptic washes