What is a boil? What are the symptoms of a boil?

A boil is a localized infection deep in the skin. A boil generally starts as a reddened, tender area. Over time, the area becomes firm and hard and tender. Eventually, the center of the abscess softens and becomes filled with infection-fighting white blood cells that the body sends from the bloodstream to eradicate the infection. This collection of white blood cells, bacteria, and proteins is known as pus. Finally, the pus "forms a head," which can be surgically opened or spontaneously drain out through the surface of the skin. A boil is also referred to as a skin abscess.

There are several different types of boils. Among these are:

• Furuncle or carbuncle: This is an abscess in the skin caused by the bacterium Staphylococcus aureus. A furuncle can have one or more openings onto the skin and may be associated with a fever or chills.



• Cystic acne: This is a type of abscess that is formed when oil ducts become clogged and infected. Cystic acne affects deeper skin tissue than the more superficial inflammation from common acne. Cystic acne is most common on the face and typically occurs in the teenage years.



• Hidradenitis suppurativa: This is a condition in which there are multiple abscesses that form under the armpits and often in the groin area. These areas are a result of local inflammation of the sweat glands. This form of skin infection is difficult to treat with antibiotics alone and typically requires a surgical procedure to remove the involved sweat glands in order to stop the skin inflammation.



• Pilonidal cyst: This is a unique kind of abscess that occurs in the crease of the buttocks. Pilonidal cysts often begin as tiny areas of infection in the base of the area of skin from which hair grows (the hair follicle). With irritation from direct pressure, over time the inflamed area enlarges to become a firm, painful, tender nodule that makes it difficult to sit without discomfort. These frequently form after long trips that involve prolonged sitting.

What causes boils to form?

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 that has become lodged in the skin. Others boils, such as those of acne, are caused by plugged sweat glands that become infected.

The skin is an essential part of our immune defense against materials and microbes that are foreign to our body. Any break in the skin, such as a cut or scrape, can develop into an abscess should it become infected with bacteria.

What does a boil look like?

Who is most likely to develop a boil?

Anyone can develop a boil. However, people with certain illnesses or medications that impair the body's immune system (the natural defense system against foreign materials or microbes) are more likely to develop boils. Among the illnesses that can be associated with impaired immune systems are diabetes and kidney failure. Diseases, such as hypogammaglobulinemia, that are associated with deficiencies in the normal immune system can increase the tendency to develop boils.

Many medications can suppress the normal immune system and increase the risk of developing boils. These medications include cortisone medications (prednisone and prednisolone) and medications used for cancer chemotherapy.

What is the treatment for a boil?

Most simple boils can be treated at home. Ideally, the treatment should begin as soon as a boil is noticed since early treatment may prevent later complications.

The primary treatment for most boils is heat application, usually with hot soaks or hot packs. Heat application increases the circulation to the area and allows the body to better fight off the infection by bringing antibodies and white blood cells to the site of infection.

As long as the boil is small and firm, opening the area and draining the boil is not helpful, even if the area is painful. However, once the boil becomes soft or "forms a head" (that is, a small pustule is noted in the boil), it can be ready to drain. Once drained, pain relief can be dramatic. Most small boils, such as those that form around hairs, drain on their own with soaking. On occasion, and especially with larger boils, the larger boil will need to be drained or "lanced" by a health-care practitioner. Frequently, these larger boils contain several pockets of pus that must be opened and drained.

Antibiotics are often used to eliminate the accompanying bacterial infection. Especially if there is an infection of the surrounding skin, the doctor often prescribes antibiotics. However, antibiotics are not needed in every situation. In fact, antibiotics have difficulty penetrating the outer wall of an abscess well and often will not cure an abscess without additional surgical drainage.

When should I seek medical attention?

Any boil or abscess in a patient with diabetes or a patient with an underlying illness that can be associated with a weakened immune system (such as cancer, rheumatoid arthritis, etc.) should be evaluated by a health-care practitioner. 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 health-care practitioner if they develop boils. (If you are not sure about your medications' effects on the immune system, your pharmacist may be able to explain to you which medicines to be concerned about.)

Any boil that is associated with a fever should receive medical attention. Increasing reddening of the nearby skin and or/formation of red streaks on the skin, the failure of a boil to "form a head," and the development of multiple boils are other symptoms that warrant a visit to a health-care practitioner.

A "pilonidal cyst," a boil that occurs between the buttocks, is a special case. These almost always require medical treatment, including drainage and packing (putting gauze in the opened abscess to assure it continues to drain). Finally, any painful boil that is not rapidly improving should be seen by a health-care practitioner.

What can be done to prevent boils (abscesses)?

There are some measures that you can take to prevent boils from forming. Good hygiene and the regular use of antibacterial soaps can help to prevent bacteria from building up on the skin. This can reduce the chance for the hair follicles to become infected and prevent the formation of boils. In some situations, your health-care practitioner may recommend special cleansers such as pHisoderm to even further reduce the bacteria on the skin. When the hair follicles on the back of the arms or around the thighs are continually inflamed, regular use of an abrasive brush (loofah brush) in the shower can be used to help break up oil plugs and build-up around hair follicles.

Pilonidal cysts can be prevented by avoiding continuous direct pressure or irritation of the buttock area when a local hair follicle becomes inflamed. At that point, regular soap and hot water cleaning and drying can be helpful.

For acne and hidradenitis suppurativa (see above), antibiotics may be required on a long-term basis to prevent recurrent abscess formation. As mentioned above, surgical resection of sweat glands in the involved skin may be necessary. Other medications, such as isotretinoin (Accutane), can be used for cystic acne and have been helpful in some patients with hidradenitis suppurativa. Recurrences are common in patients with hidradenitis suppurativa.

Finally, surgery may occasionally be needed, especially for pilonidal cysts that recur, but also for hidradenitis suppurativa. For pilonidal cysts, surgically removing the outer shell of the cyst is important to clear the boil. The procedure is typically performed in the operating room. For hidradenitis suppurativa, extensive involvement can require surgical repair by a plastic surgeon.

Boils At A Glance

• A boil, or skin abscess, is a collection of pus that forms inside the body.
• Antibiotics alone can be inadequate in treating abscesses.
• The primary treatments for boils include hot packs and draining ("lancing") the abscess but only when it is soft and ready to drain.
• If you have a fever or long-term illness, such as cancer or diabetes, or are taking medications that suppress the immune system, you should contact your health-care practitioner if you develop a boil (abscess).
• There are a number of methods that can be used to reduce the likelihood of developing some forms of boils, but boils are not completely preventable.

SourceLast Editorial Review: 1/26/2009

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