Boils and carbuncles are skin infections usually caused by Staphylococcus aureus bacteria (staph). These staph infections form pockets in the skin that are filled with pus, a fluid that includes bacteria, dead skin cells and infection-fighting white blood cells. Whether the pocket of pus is called a boil or a carbuncle depends on its location and size:
- A boil, also called a furuncle, begins as a painful infection of a single hair follicle. Boils can grow to be larger than a golf ball, and they commonly occur on the buttocks, face, neck, armpits and groin.
- A carbuncle is a deeper skin infection that involves a group of infected hair follicles in one skin location. Carbuncles often are found on the back of the neck, shoulders, hips and thighs, and they are especially common in middle-aged or elderly men. People with diabetes are more likely to develop carbuncles.
A boil looks like a red, swollen, painful bump under the skin. As the infection gets worse, a whitish tip, also called a point or head, can appear at the center of the boil. This tip is usually the area from which the boil's pus will drain. A carbuncle looks like a cluster of interconnected boils.
Whenever you have a boil or a carbuncle, you also can have a fever and feel generally sick. A fever is more likely with a carbuncle than with a single boil.
Your doctor can diagnose a boil or carbuncle by examining your skin. If you get several boils within a short period of time, your doctor may do blood tests to check for diabetes or other medical conditions that can increase your risk of repeated infections.
In many otherwise healthy people, a small boil will form a white tip (come to a head) and drain within five to seven days. However, very large boils or carbuncles can last longer and may not drain on their own. These may need to be drained by a physician, and you may need to take antibiotics.
If you have an area of skin that is prone to boils or carbuncles, keep the area clean and dry, and avoid wearing tight clothing that doesn't allow the skin to breathe. Washing daily with antibacterial soap also can help. At the earliest sign of irritation or a bump at a hair follicle, use warm compresses to open up the blocked pore and drain any early infection. If you develop signs of inflammation or infection at a hair follicle (folliculitis) as a result of shaving, you should avoid shaving in that area to prevent bacteria from being spread to other parts of the skin.
Small boils can be treated with moist heat (usually a warm, wet washcloth) applied for 20 to 30 minutes, 3 or 4 times a day. This will help the boil drain on its own. Once the boil drains, cover it with a clean bandage to protect the skin and absorb draining pus. Wash the affected area daily with antibacterial soap to prevent the infection from spreading. Anyone who helps care for the infected area should also wash his or her hands thoroughly with antibacterial soap.
Large boils and carbuncles may be treated with antibiotics. In many cases, the doctor will drain the infected area through a small incision. This will relieve pain, speed recovery and limit scar formation. If the infection is completely drained, antibiotics may not be necessary. If the infection is deep, your doctor may fill the empty pocket that contained the pus with a strip or piece of sterile gauze. The gauze can keep the incision open, which will allow pus to continue to drain. The pocket can then heal slowly, becoming more shallow over time until it is a superficial wound. You may need to return to the doctor a few times to have the gauze and dressing changed.
Call your doctor whenever you have a carbuncle, a large boil or a boil that doesn't improve after a week of warm compress treatment as described above. If you have diabetes, you should call your doctor even if you develop a small boil because you are more prone to developing serious infections. Ask to be seen immediately if a boil of any size:
- Develops in an infant
- Is located on the face, rectum, groin or spine
- Produces fever or severe pain
- Interferes with movement
- Causes swelling, red streaks or other discoloration in nearby skin
If you have been treated with antibiotics for a boil or carbuncle and your infection does not appear to be responding within one to two days, contact your doctor again. Your infection may be caused by a type of bacteria that is resistant to several commonly used antibiotics. This bacteria is called community-acquired methicillin-resistant S. aureus (community-acquired MRSA). To treat this type of infection, your doctor needs to know that your first antibiotic was not helpful. You may need to take a different kind of antibiotic.
If you have had several episodes of boils within a short period of time, visit your doctor. Your doctor can check whether an undiagnosed medical illness is affecting your body's ability to fight infections.
Most small boils heal without leaving a scar. In general, the larger the boil or carbuncle, the greater the chance that it will leave a scar. Because of this, you should see a doctor if you have a boil on your face. Antibiotic treatment and surgical drainage can help limit scar formation.
American Academy of Dermatology
P.O. Box 4014
Schaumburg, IL 60168-4014
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Insitutes of Health
1 AMS Circle
Bethesda, MD 20892-3675