A pilonidal sinus, as indicative of the name, is a narrow channel or a hole located in between the buttocks (underneath the skin). A characteristic feature of the pilonidal sinus is the presence of hair (the hair ruptures the skin and gets embedded within the sinus). A pilonidal sinus or a cyst is also known to contain skin debris, dirt. An infection of the pilonidal cyst may trigger the release of blood and pus from the cyst which is often foul smelling and associated with an excruciating pain.DR. VP SINGH CLINIC Address : J -87, Sector 41, Noida Pincode - 201303 {Near Green Valley Chowk} Tel : 7042877920, 7042877326 Email : [email protected] Mon - Thu : 06:00 PM - 08:00 PM Saturday : 06:00 PM - 08:00 PM