Boils, also called furuncles, and carbuncles are bacterial infections of hair follicles and surrounding skin that form pustules (small blister-like swellings containing pus) around the follicle. A carbuncle results when several boils merge to form a single deep abscess with several heads, or drainage points.
Boils and carbuncles are firm reddish swellings about 0.2.4 inches (50 mm) 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. Carbuncles are less common than single boils; they are most likely to form at the back of the neck. Males are more likely to develop carbuncles.
Boils and carbuncles are common problems in the general population, particularly among adolescents and adults. People who are more likely to develop these skin infections include 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
Causes and symptoms
Boils and carbuncles usually are caused by Staphylococcus aureus, a bacterium that causes an infection in an oil gland or hair follicle, or they might be caused by other bacteria or fungi. Although the surface of human skin is usually resistant to bacterial infection, S. aureus can enter through a break in the skin surfacencluding breaks caused by needle punctures for insulin or drug injections. Hair follicles that are blocked by greasy creams, petroleum jelly, or similar products are more vulnerable to infection. Bacterial skin infections can be spread by shared cosmetics or washcloths, close human contact, or by contact with pus from a boil or carbuncle.
As the infection develops, an area of inflamed tissue gradually forms a pus-filled swelling or pimple that is painful to touch. As the boil matures, it forms a yellowish head or point. It may either continue to swell until the point bursts and allows the pus to drain, or it may gradually be reabsorbed into the skin. Boils can cause a lot of pain when they occur in the ear canal, nose, or other sensitive areas. It takes between one and two weeks for a boil to heal completely after it comes to a head, discharges pus, and crusts over. The bacteria that cause the boil can spread into other areas of the skin and even into the bloodstream if the skin around the boil is squeezed. If the infection spreads, the patient will usually develop chills and fever, swollen lymph nodes (lymphadenitis), and red lines in the skin running outward from the boil. Fatigue and general discomfort are other possible symptoms.
Furunculosis is sometimes used to refer to recurrent boils. Many patients have repeated episodes of furuncu losis that are difficult to treat because their nasal passages carry colonies of S. aureus. These bacterial colonies make it easy for the patient's skin to be re-infected. They are most likely to develop in patients with diabetes, HIV infection, or other immune system disorders.
Carbuncles are formed when the bacteria infect several hair follicles that are close together. Carbunculosis is sometimes used to refer to the development of carbuncles. The abscesses spread until they merge with each other to form a single large area of infected skin with several pus-filled heads. Patients with carbuncles may also have a low-grade fever or feel generally unwell.
The diagnosis of boils and carbuncles is usually made by the patient's primary care doctor on the basis of visual examination of the skin. In some cases involving recurrent boils on the face, the doctor may consider acne as a possible diagnosis, but, for the most part, boils and carbuncles are not difficult to distinguish from other skin disorders.
S. aureus can easily be cultured in the laboratory if the doctor needs to rule out inclusion cysts or deep fungal infections that gardeners sometimes get. The doctor can take a culture from pus taken from the boil or carbuncle to confirm the diagnosis of a staphylococcal infection. He or she can also culture the patient's nasal discharge to test for the presence of a S. aureus colony.
Some boils heal spontaneously before progressing to pustules. Often, they become pustules that eventually burst, drain and then heal by themselves. Boils usually occur and are healed in about two weeks. Patients who have boils that take longer than two weeks to heal should be see a doctor. Other reasons to seek professional medical advice are if boils recur, are located on the spine or the middle of the face, or are accompanied by symptoms such as fever. These boils are most at risk for spreading the infection.
Patient and family education
Patient education is an important part of the treatment of boils and carbuncles. Patients need to be warned against picking at or squeezing boils because of the danger of spreading the infection into other parts of the skin or bloodstream. It is especially important to avoid squeezing boils around the mouth or nose because infection in these areas can be carried to the brain. Patients should also be advised about keeping the skin clean, washing their hands carefully before and after touching the boil or carbuncle, avoiding the use of greasy cosmetics or creams, and keeping their towels and washcloths separate from those of other family members. Some doctors may recommend an antiseptic soap or gel for washing the infected areas. People who have boils often benefit from applying warm compresses several times a day to help the boils come to a head and drain.
If the patient has had several episodes of furunculosis, the doctor may examine family members or close contacts to see if they are carriers of S. aureus. In many cases, some of the family members may also need treatment for boils or carbuncles. Skin infection and re-infection involving small groups or clusters of people are being reported more frequently in the United States.
Boils are usually treated with application of topical antibiotic creams, such as clindamycin or polymyxin, following the use of hot compresses to help the infection drain, which speeds healing.
Carbuncles and furunculosis are usually treated with oral antibiotics as well as topical antibiotic creams or ointments. The specific medications that are given are usually dicloxacillin (Dynapen) or cephalexin (Keflex); erythromycin may be given to patients who are allergic to penicillin. The usual course of oral antibiotics is 50 days, although patients with recurrent furunculosis may be prescribed oral antibiotics for longer periods. Furunculosis is also treated with a combination of dicloxacillin and rifampin (Rifadin). Still, many experts agree that topical antibiotics help very little once the boil has formed.
Patients with bacterial colonies in their nasal passages are often given mupirocin (Bactroban) to apply directly to the lining of the nose.
Boils and carbuncles that are very large, or that are not draining, may be opened by a doctor with a sterile needle or surgical knife to allow the pus to drain. The patient is usually administered a local anesthetic if a knife is used as surgical treatment of boils is painful, and frequently leaves noticeable scars.
Naturopathic practitioners usually recommend changes in the patient's diet as well as applying herbal poultices to the infected area. The addition of zinc supplements and vitamin A to the diet has been reported to be effective in treating boils. The application of a paste or poultice containing goldenseal root (Hydrastis canadensis) is recommended by naturopaths on the grounds that goldenseal helps to kill bacteria and reduce inflammation.
Homeopaths maintain that taking the proper homeopathic medication in the first stages of a boil or carbuncle will bring about early resolution of the infection and prevent pus formation. The most likely choices are Belladonna or Hepar sulphureus. If the boil has already formed, Mercurius vivus or Silica may be recommended to bring the pus to a head.
A variety of herbal remedies can be applied topically to boils to fight infection. These include essential oils of bergamot (Citrus bergamia), chamomile (Matricaria recutita), lavender (Lavandula officinalis), and sage (Salvia officinalis), as well as tea tree oil (Melaleuca spp.). Herbalists also recommend washing the skin with a mixture of goldenseal and witch hazel. To fight the inflammation associated with boils, herbalists suggest mixing marsh mallow (Althaea officinalis) ointment, tinctures (herbal solutions made with alcohol) of blue flag (Iris versicolor) or myrrh (Commiphora mol mol), and slippery elm (Ulmus fulva) into a poultice.
The prognosis for most boils is excellent, although some patients suffer from recurrent carbuncles or furunculosis. In addition, though the spread of infection from boils is relatively unusual, there have been deaths reported from brain infections caused by squeezing boils on the upper lip or in the tissue folds at the base of the nose. Some patients also experience permanent scarring of the skin.
Health care team roles
Nurses help to educate patients about how to avoid infection of boils, ensure proper healing, and prevent recurrence. The nurse might also take a culture of the affected area to confirm the doctor or nurse practitioner's diagnosis. If in-office surgery to drain the boil is indicated, the nurse might assist in preparation for the procedure and during the procedure.
There are some precautions that people can take to minimize the risk of developing bacterial skin infections:
- Cleanse the skin properly with soap and water, and take showers rather than tub baths.
- Do not share washcloths, towels, or facial cosmetics with others.
- Cut down on greasy or fatty foods.
- Always wash hands before touching the face.
- Consider using antiseptic soaps and shower gels.
- Consult a doctor if furunculosis is a persistent problemt may indicate an underlying disease such as diabetes.
Abscess localized collection of pus in the skin or other body tissue.
Carbuncle large, deep skin abscess formed by a group or cluster of boils.
Folliclehe small sac at the base of a hair shaft. The follicle lies below the skin surface.
Furunculosis condition in which the patient suffers from recurrent episodes of boils.
Pustule small raised pimple or blister-like swelling of the skin that contains pus.
Berger, Timothy G. "Skin and Appendages." In Current Medical Diagnosis and Treatment 1998, edited by Lawrence M. Tierney, Jr. et al. Stamford, CT: Appleton and Lange, 1997.
Hacker, Steven M. "Common Bacterial and Fungal Infections of the Integument." In Current Diagnosis 9, edited by Rex B. Conn et al. Philadelphia: W.B. Saunders, 1997.
Rasmussen, James E. "Bacterial Infections of the Skin." In Conn's Current Therapy, edited by Robert E. Rakel. Philadelphia: W.B. Saunders, 1998.
"Furuncle." WebMD. 1999. <<a href="http://my.webmld.com/content/asset/adam_disease_boils">http://my.webmld.com/content/asset/adam_disease_boils>.
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