A pilonidal sinus is a small hole at the top of your bottom, between your buttocks. Treatment is usually only needed if it becomes infected.
An infected pilonidal sinus is red, painful and may bleed or leak pus.
An infected pilonidal sinus is treated with antibiotics. The pus may also need to be drained. In some cases, you may need surgery.
It's not clear what causes a pilonidal sinus. A skin problem, pressure or friction may cause hair between the buttocks to be pushed inwards.
Page last reviewed: 06/12/2017
Next review due: 06/12/2020