Pilonidal cysts contain skin debris and hair inside a pocket that forms in the skin, according to Mayo Clinic. The most common location for these cysts is the highest point of the cleft of the buttocks, close to the tailbone. The most frequent cause is hair embedding in the skin.
In some cases, pilonidal cysts develop infections and form abscesses. When this happens, the pain is often significant. Surgical treatment involves either draining the cyst with a small cut or removing the cyst entirely. Pilonidal cysts most often affect young men, and they frequently recur. Sitting for long periods of time increases the risk of a pilonidal cyst, states Mayo Clinic.