A boil is an infection that affects groups of hair follicles and nearby skin tissue.
Related conditions include folliculitis, an inflammation of one or more hair follicles, and carbunculosis, a skin infection that often involves a group of hair follicles.
Boils are very common. They are most often caused by the bacteria Staphylococcus aureus. They can also be caused by other types of bacteria or fungi found on the skin's surface. Damage to the hair follicle allows the infection to grow deeper into the follicle and the tissues under it.
Boils may occur in the hair follicles anywhere on the body. They are most common on the face, neck, armpit, buttocks, and thighs. You may have one or many boils. The condition may occur only once or it can be a long-lasting (chronic) problem.
A boil may begin as tender, pinkish-red, and swollen, on a firm area of the skin. Over time, it will feel like a water-filled balloon or cyst.
Pain gets worse as it fills with pus and dead tissue. Pain lessens when the boil drains. A boil may drain on its own. More often, the boil needs to be opened to drain.
The main symptoms of a boil include:
Other symptoms may include:
Boils may heal on their own after a period of itching and mild pain. More often, they become more painful as pus builds up.
Boils usually need to open and drain in order to heal. This most often happens within 2 weeks. You should:
You may need to have surgery to drain deep or large boils. Get treatment from your provider if:
It is important to keep a boil clean. To do this:
Your provider may give you antibiotics to take by mouth or a shot, if the boil is very bad or comes back.
Antibacterial soaps and creams cannot help much once a boil has formed.
Some people have repeated boil infections and are unable to prevent them.
Boils in areas like the ear canal or nose can be very painful.
Boils that form close together may expand and join, causing a condition called carbunculosis.
These complications may occur:
Call your provider if boils:
The following may help prevent the spread of infection:
Habif TP. Bacterial infections. In: Habif TP, ed. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Philadelphia, PA: Elsevier; 2016:chap 9.
Pallin DJ. Skin infections. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 129.