Boils (medically called furuncles) are skin sores usually caused by bacteria that infect hair follicles and the sebaceous (oil) glands deeper in the skin. At first, they may look like small red pimples but can become quite tender and painful and can grow to the size of a golf ball. After a few days, they form pus-filled “heads,” which eventually rupture, drain, and then heal over, sometimes leaving a scar.
You can get boils anywhere you have hair—notably your armpits, buttocks, and groin, as well as your neck and face. Usually they form on areas that are moist or subjected to pressure and friction (as may occur in bicycle riding) or other irritation, and they tend to occur more frequently in warmer months.
A cluster of boils, referred to as a carbuncle, indicates a spread of infection laterally under the skin; it takes longer to heal and usually requires medical attention.
The culprit behind boils is typically Staphylococcus aureus, a bacterium that commonly resides on skin and can enter the body through cuts, scratches, or other breaks (including microscopic ones). Though boils are usually a minor ailment, one worry is that if bacteria get into the bloodstream, this can lead to sepsis (“blood poisoning”) and infect the heart and other organs. Another worry is if the infection is caused by MRSA (methicillin-resistant Staphylococcus aureus), which is widespread in hospitals and the general population and is more difficult to treat. According to a paper in the British Journal of Dermatology in 2012, the incidence of boils has been rising in the U.S., with most new cases attributed to MRSA.
Anyone can develop boils, but they are more common in people who have a suppressed immune system (due to illness or medication), diabetes, skin diseases (such as eczema), or household members with boils (since the bacteria spread easily). Recurrences are common and are associated with poor personal hygiene and having Staphylococcus aureus present in nasal passageways.
How to relieve and prevent boils
Boils usually go away on their own within two weeks or so. Warm, moist compresses can provide some relief and help bring the infection to a head. Don’t scratch, squeeze, or break a boil, though, since that can spread and worsen the infection. When the boil erupts and is draining, keep it covered with a bandage. Always wash your hands well after touching a boil or its pus to avoid spreading the bacteria.
If a boil becomes more painful and keeps getting bigger—or if you develop a fever—see your health care provider. It may have to be lanced and drained. Under certain circumstances, you may need an antibiotic. You should also get medical attention if you have a boil above your lips, on your nose, or in your ear, since this can be more dangerous.
If you get recurrent boils or are immune-compromised, your doctor may take a culture to see if you are a staph carrier—and if you are, you may be advised to bathe regularly with antiseptic cleanser (chlorhexidine, for example) or use a topical nasal antibiotic.
To prevent boils, wash your hands often (which you should be doing anyway); avoid sharing towels, razors, tweezers, or other personal items; cleanse even minor cuts and scrapes; wear wickable (breathable) clothing while exercising; and always shower after a workout.
Also see Are Sebaceous Cysts Dangerous?