Pilonidal sinus—also called a pilonidal cyst—is a skin infection that occurs in or around the crease of your buttocks. This condition happens when hair, skin cells, and dirt clog a hair follicle, ...

Pilonidal cysts typically develop above the cleft of the buttocks. These swollen lumps contain hair or other debris. They occur when small holes in the skin, known as pilonidal sinuses, become ...

It often starts as a sore spot you assume is a zit, ingrown hair, or minor irritation. Then it gets worse. Sitting becomes uncomfortable. Pressure builds. Sometimes there’s swelling, drainage, or even ...