Definition

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

See also:

Alternative Names

Furuncle

Causes, incidence, and risk factors

Boils are very common. They are generally caused by the bacteria 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 tissue underneath.

Boils may occur in the hair follicles anywhere on the body. They are most common on the face, neck, armpit, buttocks, and thighs. There can be one or many boils.

Symptoms

A boil may begin as a tender, pinkish-red, swollen, firm area in the skin. Over time, it will feel like a water-filled balloon or cyst.

Pain gets worse as it fills with pus and dead tissue, and improves as it drains. It may drain on its own. More often the patient or someone else opens the boil.

The boil:

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

Other symptoms may include:

Fatigue
Fever
General ill-feeling
Itching before the boil develops
Skin rednessaround the boil

Signs and tests

The health care provider can usually diagnose a boil based on how it looks. A culture may show staphylococcus or other bacteria.

Treatment

Boils may heal on their own after a period of itching and mild pain. More often, they increase in discomfort as pus collects.

Boils usually must open and drain before they will heal. This usually occurs in less than 2 weeks.

Warm, moist compresses help boils drain, which speeds healing. Gently soak the area with a warm, moist cloth several times each day.
Never squeeze a boil or try to cut it open at home. This can spread the infection and make it worse.
When the boil finally does burst and drain, continue to put warm, wet compresses on the area.

Deep or large boils may need to be drained with surgery by a health care provider. Treatment by a health care provider is needed if:

A boil lasts longer than 2 weeks
A boil comes back
The boil is on the spine or the middle of the face
The boil occurs with a fever or other symptoms, because the infection may spread and cause complications

Careful hygiene is important:

Clean draining boils often.
Wash your hands very well after touching a boil.
Do not re-use or share washcloths or towels. Wash clothing, washcloths, towels, and sheets or other items that contact infected areas in very hot (preferably boiling) water.
Change dressings often and throw them out with the drainage, such as by placing them in a bag that can be closed tightly before throwing it out.

Antibacterial soaps and antibiotics placed on the skin are of little help once a boil has formed. Antibiotics taken by mouth or given as a shot may help a more severe infection or if the boil returns.

Expectations (prognosis)

Some people have repeated abscesses and are unable to prevent them.

Boils can be very painful if they occur in areas like the ear canal or nose. A health care provider should treat boils of the nose.

Boils that form close together may expand and join, causing a condition called carbunculosis.

Complications

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

Calling your health care provider

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

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

Prevention

The following may help prevent the spread of infection:

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

References

Habif TM. Bacterial infections. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 9.

Reviewed By

Review Date: 10/28/2010

Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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