Pilonidal disease is an infection of the skin above the crease between the buttocks. In this area, the infected skin appears as a small dimple or pit, called a sinus, which usually contains hair. If the sinus becomes infected, it can cause a lot of pain and become very swollen.

Pilonidal disease often has no symptoms unless the sinus becomes infected. If this happens, redness or swelling may appear near the top of the crease of your buttocks. In addition, cloudy fluid or blood may drain from the infected sinus, and it may be difficult or painful for you to walk.

Your doctor may diagnose pilonidal disease 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.

Your doctor can usually treat an acute infection in the office and help you to feel better. Long-term treatment, though, usually requires an operation.