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Diseases and Conditions
Boils and carbuncles
From MayoClinic.com
Special to CNN.com

Introduction

Boils and carbuncles are painful, pus-filled bumps that form under your skin when bacteria infect and inflame one or more of your hair follicles.

Boils usually start as red, tender lumps. The lumps quickly fill with pus, growing larger and more painful until they rupture and drain. Although some boils disappear a few days after they occur, most take about two weeks to heal.

Boils can occur anywhere on your skin, but appear mainly on your face, neck, armpits, buttocks or thighs — hair-bearing areas where you're most likely to sweat or experience friction. Sometimes boils occur in clusters called carbuncles. Although anyone can develop boils and carbuncles, people who have diabetes, a suppressed immune system, or acne or other skin problems are at increased risk.

You can usually care for a single boil at home, but don't attempt to lance or squeeze it — that may spread the infection. Call your doctor if a boil or carbuncle is extremely painful, lasts longer than two weeks or occurs with a fever. In that case, you may need antibiotics or surgical drainage to clear the infection of boils and carbuncles.

Signs and symptoms

A boil usually appears suddenly as a painful pink or red bump that's generally not more than 1 inch in diameter. The surrounding skin also may be red and swollen.

Within a few days, the bump fills with pus. It grows larger and more painful for about five to seven days, sometimes reaching golf ball size before it develops a yellow-white tip that finally ruptures and drains. Boils generally clear completely in about two weeks. Small boils usually heal without scarring, but a large boil may leave a scar.

A carbuncle is a cluster of boils that often occurs on the back of the neck, shoulders or thighs, especially in older men. Carbuncles cause a deeper and more severe infection than single boils do. In addition, carbuncles develop and heal more slowly and are likely to leave a scar. Carbuncles sometimes occur with a fever.

Boils and carbuncles often resemble the inflamed, painful lumps caused by cystic acne. But compared with acne cysts, boils are usually redder or more inflamed around the border and more painful.

Causes

Boils usually form when one or more hair follicles — the tube-shaped shafts from which hair grows — become infected with staph bacteria (Staphylococcus aureus). These bacteria, which normally inhabit your skin and sometimes your throat and nasal passages, are responsible for a number of serious diseases, including pneumonia, meningitis, urinary tract infections and endocarditis — an infection of the lining of your heart. They're also a major cause of hospital-acquired infections and food-borne illnesses.

Staph bacteria that cause boils generally enter through a cut, scratch or other break in your skin. As soon as this occurs, specialized white blood cells called neutrophils rush to the site to fight the infection. This leads to inflammation and eventually to the formation of pus — a mixture of old white blood cells, bacteria and dead skin cells.

Risk factors

Although anyone — including otherwise healthy people — can develop boils or carbuncles, the following factors can increase your risk:

  • Poor general health. Having chronic poor health makes it harder for your immune system to fight infections.
  • Diabetes. This disease can make it more difficult for your body to fight infection, including bacterial infections of your skin.
  • Clothing that binds or chafes. The constant irritation from tight clothing can cause breaks in your skin, making it easier for bacteria to enter your body.
  • Other skin conditions. Because they damage your skin's protective barrier, skin problems, such as acne and dermatitis, make you more susceptible to boils and carbuncles.
  • Immune-suppressing medications. Long-term use of corticosteroids, such as prednisone or other drugs that suppress your immune system, can increase your risk.

When to seek medical advice

You usually can care for a single, small boil yourself. But see your doctor if a boil occurs on your face or spine or if you have:

  • A boil that worsens rapidly or is extremely painful
  • Boils that are very large, haven't healed in two weeks or are accompanied by a fever
  • Frequent boils
  • Red lines radiating from a boil, which may be a sign that the infection has entered your bloodstream
  • A condition that suppresses your immune system, such as an organ transplant or HIV infection

Children and older adults who develop one or more boils should also receive medical care.

Screening and diagnosis

Doctors usually diagnose a boil simply by looking at your skin, but sometimes they take a sample of pus to check for the bacteria it contains. If you have recurring infections, you may be tested for diabetes or other illnesses that weaken your immune system.

Complications

In some cases, bacteria from a boil can enter your bloodstream and travel to other parts of your body. The spreading infection, commonly known as blood poisoning (septicemia), can rapidly become life-threatening.

Initially, blood poisoning causes signs and symptoms such as chills, a spiking fever, a rapid heart rate and a feeling of being extremely ill. But the condition can quickly progress to shock, which is marked by falling blood pressure and body temperature, confusion, clotting abnormalities and bleeding into the skin. Blood poisoning is a medical emergency — untreated, it can be fatal.

Another potentially serious problem is the emergence of a drug resistant strain of Staphylococcus aureus. Once mainly confined to hospitals, methicillin-resistant Staphylococcus aureus (MRSA) now affects increasing numbers of military recruits, prison inmates, athletes and even children. According to the Centers for Disease Control and Prevention, about 1 percent of Americans carry MRSA on their bodies.

MRSA is highly contagious and spreads rapidly in crowded or unhygienic situations, or where athletic equipment or towels are shared. Although it responds well to several antibiotics, MRSA is resistant to penicillin, and can be very difficult to treat.

Treatment

Your doctor may drain a large boil or carbuncle by making a small incision in the tip. This relieves pain, speeds recovery and helps lessen scarring. Deep infections that can't be completely cleared may be covered with sterile gauze so that pus can continue to drain. Sometimes your doctor may prescribe antibiotics to help heal severe or recurrent infections.

Prevention

Although it's not always possible to prevent boils, especially if you have a compromised immune system, the following measures may help you avoid staph infections:

  • Thoroughly clean even small cuts and scrapes. Wash well with soap and water and apply an over-the-counter antibiotic ointment.
  • Avoid constricting clothing. Tight clothes may be stylish, but make sure they don't chafe your skin.

Self-care

The following measures may help the infection heal more quickly and prevent it from spreading:

  • Apply a warm washcloth or compress to the affected area. Do this for at least 10 minutes every few hours. If possible, first soak the cloth or compress in warm salt water. This helps the boil rupture and drain more quickly. To make salt water, add 1 teaspoon of salt to 1 quart of boiling water and cool to a comfortable temperature.
  • Gently wash the boil two to three times a day. After washing, apply an over-the-counter antibiotic and cover with a bandage.
  • Never squeeze or lance a boil. This can spread the infection.
  • Wash your hands thoroughly after treating a boil. Also, launder clothing, towels or compresses that have touched the infected area.

Complementary and alternative medicine

Tea tree oil, which is extracted from the leaves of the Australian tea tree (Melaleuca alternifolia), has been used for centuries as an antiseptic, antibiotic and antifungal agent. It may help relieve discomfort and speed healing.

For best results, apply the oil to a boil several times a day. The oil can cause allergic reactions in some people, so be sure to stop using it if you have any problems.

October 17, 2006

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