Pilonidal disease is an infection caused by a hair that injures the skin at the top of the cleft between the buttocks.

For unknown reasons, sometimes a hair irritates and grows into the skin, forming a cavity that may thus contain hair. Such a cavity is called a pilonidal cyst and typically forms at the top of the cleft between the buttocks. The cyst may cause no symptoms, or it may become infected. If the infection causes a collection of pus to form, it is termed a pilonidal abscess. A pilonidal sinus is a chronic draining wound at the site.

Pilonidal disease usually occurs in young, hairy, white men but can also occur in women. A pilonidal abscess causes pain, redness, and swelling. Sometimes pus drains spontaneously from the abscess. To distinguish pilonidal disease from other infections, a doctor looks for tiny holes in or next to the infected area (pits).

Generally, a pilonidal abscess must be cut and drained by a doctor. Usually, a pilonidal sinus must be treated surgically.

Last full review/revision May 2012 by Parswa Ansari, MD