Boils, Abscesses, Carbuncles

Boils are infected, pus-filled swellings in the skin that are often located in or near hair follicles.  They are most often found on the back of the neck and in other moist areas of the body like the armpits and groin, but may be anywhere on the body.  Sometimes several boils form close together in a cluster.  A carbuncle is formed when several boils merge to form a single deep abscess with several heads or drainage points.  An abscess can be so deep that it may not surface for a long time.

Boils and carbuncles are firm reddish swellings about 5-10mm across that are slightly raised above the skin surface.  They are sore to the touch.  A boil usually has a visible central core of pus; a carbuncle is larger and has several visible heads.  Boils occur most commonly on the face, back of the neck, buttocks, upper legs and groin area, armpits, and upper torso.

There are several different types of boils, including:

Comparison between an ordinary boil with one opening onto the skin (left), and a carbuncle with many openings (right)

Furuncle or carbuncle: An abscess in the skin caused by the bacteria Staphylococcus aureus.  It can have one or more openings onto the skin and may be associated with a fever or chills.  They are less common than single boils; they are most likely to form at the back of the neck and in males.  Carbuncles can form in the same areas as boils, and may also form on the scalp, face, and buttocks.  Furunculosis is a word that is sometimes used to refer to recurrent boils.  Many patients have repeated episodes of furunculosis that are difficult to treat because their nasal passages carry colonies of Staphylococcus aureus.  These bacterial colonies make it easy for the patient's skin to be reinfected.

Folliculitis: A milder version of boils.  This is an infection of hair follicles, usually with Staph bacteria.  These often itch more than hurt.  The appearance is similar to acne pustules.

Cystic acne: A type of abscess formed when oil ducts become clogged and infected.  Cystic acne is most common in the teenage years.

Hidradenitis suppurativa: An uncommon illness of unknown cause in which there are multiple abscesses that form under the armpits, in the groin area, or under the breasts.  These areas are a result of local inflammation of the sweat glands.

Pilonidal cyst: A type of abscess that occurs in the crease of the buttocks.  These frequently form after long trips that involve sitting.

Causes and Development; Contributing Risk Factors

There are many causes of boils.  Some boils can be caused by an ingrown hair.  Others can form as the result of a splinter or other foreign material lodged in the skin.  Others, such as those of acne, are caused by plugged sweat glands that become infected.  Any break in the skin such as a cut or scrape can develop into an abscess if it becomes infected with bacteria.

Boils and carbuncles are more likely to develop in those with:

• Diabetes, especially when treated by injected insulin
• Alcoholism or drug abuse
• Poor personal hygiene
• Crowded living arrangements
• Jobs or hobbies that expose them to greasy or oily substances, especially petroleum products
• Allergies or immune system disorders, including HIV infection
• Family members with recurrent skin infections

Signs and Symptoms

A boil, or skin abscess, is a localized infection deep in the skin.  A boil generally starts as an itchy, red, painful lump.  Over time, the area becomes firm and hard.  Usually within 24 hours, the lump fills with pus and takes on a round appearance with a yellow-white tip.  Eventually, the center of the abscess softens; the pus forms a "head" and drains out through the skin.

There may be swelling around the boil as well as swelling of any lymph nodes near the boil.

Treatment and Prevention

Most simple boils can be treated at home.  The treatment should start as soon as a boil is noticed since early treatment may prevent later problems.

Proper disinfection is important when squeezing a boil: the infectious material inside is often ejected some distance

Since releasing the pus in a boil can lead to more infection, puncturing it at home is not usually advised.  If you do lance it, or if it bursts, make sure to sterilize the surrounding area carefully, washing hands after touching the area.

Medical treatment by a healthcare provider may include lancing or puncturing the boil to release the pressure and allow for drainage.  Antibiotics may be prescribed to stop the infection.

Medications such as isotretinoin (Accutane) can be used for cystic acne; this has been helpful for some patients with hidradenitis suppurativa.

There are some measures that you can take to prevent abscesses from forming.  Practicing good hygiene habits minimizes the frequency of recurring boils and prevents the spread of infection.  This includes not picking at boils, using clean towels after each bath or shower, and cleaning the skin with an antiseptic / antibacterial soap such as Betadine.  Antibacterial soaps may help prevent bacteria build up on the skin and therefore reduce the chance for an abscess to form.

Prognosis; Seek medical attention if...

Boils may take from 10 to 25 days to heal.  In most cases, a boil will not heal until it bursts and drains.  This can take as long as 5 to 7 days.  A single boil can usually be cared for at home and does not require a trip to the doctor.

Recurrences are common in patients with hidradenitis suppurativa.

Any boil or abscess in a patient with diabetes or a patient with an underlying illness (such as cancer, rheumatoid arthritis, etc.)  should be seen by a doctor.  Additionally, many medicines, especially prednisone, that suppress the immune system (the natural infection-fighting system of the body) can complicate what would be an otherwise simple boil.  Patients who are on such medications should consult their doctor if they develop boils.

Any boil that is associated with a fever should receive medical attention.  A pilonidal cyst is a special case and almost always requires medical treatment including drainage and packing (putting gauze in the open abscess to assure it continues to drain).  Finally, any painful boil that is not rapidly improving should be seen.

You should also see a doctor if:

• a boil develops in a child or a sick or elderly person
• a boil develops on the face near the eyes or nose
• a boil becomes extremely large or painful
• a cluster of boils form or you have an abscess
• boils become increasingly common
• red lines spread out from the center of the boil
• the boil is extremely tender
• fever and chills develop
• lymph nodes begin to swell that are located in other areas of the body from where the original lymph node swelling occurred.