What is pilonidal disease?

Pilonidal disease is a chronic infection in the skin slightly above the crease between the buttocks. It develops in a cyst (pilonidal cyst) at the top of or next to the crease between the buttocks (overlying the sacrum). The cyst may look like a small dimple (called a "pit" or "sinus"). Hair may protrude from the pit, and several pits may be seen.

See a picture of a pilonidal cyst.

A pilonidal cyst can be painful enough to make sitting or walking difficult, and in some cases pus or blood may drain from the pit.

What causes a pilonidal cyst?

At one time, most experts believed pilonidal cysts were present at birth (congenital). But now experts think a pilonidal cyst may form in three ways. Some are probably present at birth. However, most experts now believe that the cysts develop later in life in one of two ways, or a combination of the two:

• A pilonidal cyst may form when a hair follicle (the sac from which a hair grows) in the skin becomes irritated or stretched. This may be due to exercise that affects the buttocks area (such as horseback riding or cycling), tight clothing around the buttocks, heat, or extensive sweating. The hair follicle becomes blocked and infected and then swells and ruptures into the surrounding tissue, forming an abscess. Continued exercise or walking often pulls hair into the abscess.
• In some people, particularly those with coarse or stiff hair, a loose hair may become trapped in the crease of the buttocks. The hair can poke into the skin, especially if there is already a stretched or irritated hair follicle. Walking and exercise can pull the hair further into the skin. A cyst then forms around the hair and can become infected.

What are the symptoms?

Pilonidal disease often has no symptoms. If the cyst becomes infected (an infected cyst is called an abscess), you may have redness or swelling near the top of the crease of your buttocks, cloudy fluid or blood draining from the abscess, and sometimes difficulty walking or sitting because of pain from the area of the abscess.

How is it diagnosed?

Pilonidal disease is diagnosed by your doctor after visually examining and gently feeling the area around the crease in the buttocks to check for redness, warmth, and swelling. No other tests are usually needed.

What is the treatment?

Treatment for pilonidal disease can include keeping the area around the crease of the buttocks clean with antibacterial soap and possibly taking antibiotics to control the infection. Using an alcohol swab 2 to 3 times a day when the pilonidal area begins to get irritated can help manage the infection. Treatment also may involve draining the cyst, and sometimes surgery to either open or remove the cyst. Between 60% and 80% of people heal after a minor procedure to open and clean the infected cyst (abscess).¹

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