Pilondal Sinus or PNS occurs when a small cyst or abscess occurs in the cleft on top of the buttocks. It usually is a combination of hair, dirt and debris. It can be extremely painful and is easily infected. There is a high chance of pus, blood and foul odour. It is most commonly observed in men, young adults and people with jobs that require them to sit for long hours.
PNS does not have a particular cause that one can pinpoint to but it is supposed to be caused by a number of factors including sitting for long hours, hormone changes, hair growth, friction from clothes etc. Sitting for a long time can cause hair growing in that area to burrow back into the skin. The body then unleashes immune response against it like it would when it senses a splinter. Thus, a cyst forms around the hair.
There are both dormant and active pilonidal sinuses. The most common symptoms for which people seek pilonidal sinus treatment is pain while sitting or standing, swelling of cyst, reddened or sore skin around cyst area, pus or blood from cyst, protruding hair, one or more sinus tracts i.e. holes in the skin etc. It is best to seek treatment before a dormant pilonidal sinus becomes active.