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, ...

Also known as a pilonidal cyst, the condition forms when a sac of tissue fills with air or fluid in the crease of your buttocks. Pilonidal cyst, doctors say, is mostly caused by a skin infection.

From razor bumps to painful deep cysts, here’s how to identify what you’re dealing with and the science-backed solutions for smooth, clear skin Ingrown hair cysts rank among the most frustrating skin ...