A boil is a painful, pus-filled bump that forms under your skin when bacteria infect and inflame one or more of your hair follicles. A carbuncle is a cluster of boils that form a connected area of infection under the skin.
Boils (furuncles) usually start as red, tender bumps. The bumps quickly fill with pus, growing larger and more painful until they rupture and drain. Areas most likely to be affected are the face, back of the neck, armpits, thighs and buttocks.
You can usually care for a single boil at home. But don't attempt to prick or squeeze it — that may spread the infection.
A boil is a painful, pus-filled bump under your skin — the result of a bacterial infection of one or more hair follicles.
A carbuncle is a cluster of boils — painful, pus-filled bumps — that form a connected area of infection under the skin.
Boils can occur anywhere on your skin, but appear mainly on the face, back of the neck, armpits, thighs and buttocks — hair-bearing areas where you're most likely to sweat or experience friction. Signs and symptoms of a boil usually include:
A carbuncle is a cluster of boils that form a connected area of infection. Compared with single boils, carbuncles cause a deeper and more severe infection and are more likely to leave a scar. People who have a carbuncle often feel unwell in general and may experience a fever and chills.
You usually can care for a single, small boil yourself. But see your doctor if you have more than one boil at a time or if a boil:
Most boils are caused by Staphylococcus aureus, a type of bacterium commonly found on the skin and inside the nose. A bump forms as pus collects under the skin. Boils sometimes develop at sites where the skin has been broken by a small injury or an insect bite, which gives the bacteria easy entry.
Although anyone — including otherwise healthy people — can develop boils or carbuncles, the following factors can increase your risk:
Rarely, bacteria from a boil or carbuncle can enter your bloodstream and travel to other parts of your body. The spreading infection, commonly known as blood poisoning (sepsis), can lead to infections deep within your body, such as your heart (endocarditis) and bone (osteomyelitis).
It's not always possible to prevent boils, especially if you have a weakened immune system. But the following measures may help you avoid staph infections:
Your doctor will likely be able to diagnose a boil or carbuncle simply by looking at it. A sample of the pus may be sent to the lab for testing. This may be useful if you have recurring infections or an infection that hasn't responded to standard treatment.
Many varieties of the bacteria that cause boils have become resistant to certain types of antibiotics. So lab testing can help determine what type of antibiotic would work best in your situation.
You can generally treat small boils at home by applying warm compresses to relieve pain and promote natural drainage.
For larger boils and carbuncles, treatment may include:
For small boils, these measures may help the infection heal more quickly and prevent it from spreading:
You're likely to see your family doctor or primary care provider first, who may then refer you to a specialist in skin diseases (dermatologist) or infectious diseases.
List all your signs and symptoms and when they first occurred. Record how long the bumps lasted and if any recurred. Make a list of all medications — including vitamins, herbs and over-the-counter drugs — that you're taking. Even better, take the original bottles and a list of the doses and directions.
For boils and carbuncles, some basic questions to ask your doctor include:
Your doctor is likely to ask you a number of questions, such as: