Pilonidal sinus

A pilonidal sinus is a small hole or tunnel in the skin at the top of the buttocks, where they divide (the cleft). It does not always cause symptoms and only needs to be treated if it becomes infected.

Check if you have an infected pilonidal sinus

Most people with a pilonidal sinus do not notice it unless it becomes infected and causes symptoms.

An infection will cause pain and swelling, and a pus-filled skin abscess can develop.

See what an infected pilonidal sinus looks like
An infected pilonidal sinus in the cleft at the top of the buttocks.
An infected pilonidal sinus is red, painful and may bleed or leak pus

Non-urgent advice: See a GP if:

  • you have a small lump at the top of your bottom (between your buttocks) that's painful, red, bleeding or leaking pus

These symptoms can develop quickly, often over a few days. They're signs of infection and need to be treated.

A pilonidal sinus that's not infected

Treatment is not needed if there are no signs of infection. A "watch and wait" approach will be recommended.

It's very important to keep the area between your buttocks clean by showering or bathing regularly.

Do not shave the affected area unless a GP advises you to.

Treatments for an infected pilonidal sinus

Treatment for an infected pilonidal sinus will depend on:

A pilonidal sinus abscess will need treatment with antibiotics. The pus inside will also probably need to be drained.

There are a number of treatment options for a pilonidal sinus that keeps coming back and that's painful, bleeding or leaking discharge. Your doctor will discuss these with you.

In most cases you'll be offered painkillers, such as paracetamol and anti-inflammatories to help reduce pain and swelling.

Incision and drainage

Hospital procedure for an uncomplicated abscess. A small hole is made in the abscess so the pus can be drained.

Wide excision and open healing

Surgery for a large or repeatedly infected sinus. The sinus is cut out and some surrounding skin removed. The wound is left open to heal naturally.

Excision and wound closure, often with flattening of the groove between the buttocks

Surgery for a large or repeatedly infected sinus. The sinus is removed and an oval-shaped flap of skin cut out on either side of it. The 2 sides are stitched together.

Endoscopic ablation for a pilonidal sinus

An endoscope (a thin, flexible tube with a camera on the end) is used to give a clear view of the affected area.

Hair and infected tissue are removed, and the sinus cleaned with a special solution. Heat is used to seal the sinus.

Plastic surgery is sometimes used if the area being treated is particularly large. The sinus is removed and the surrounding skin reconstructed.

Less invasive procedures, like injection with fibrin glue, are also available in some places.


You'll have a follow-up appointment with your specialist after your surgery. This is usually about 6 weeks later, but may be slightly longer.

What to do after your operation


  • keep the affected area clean

  • wear comfortable, loose-fitting cotton underwear

  • eat plenty of fibre to make going to the toilet easier and avoid straining


  • do not lift heavy objects or do strenuous exercise for the first week or so

  • do not ride a bike for 6 to 8 weeks

  • do not go swimming until your wound has completely healed

How soon you can return to work depends on:

Most people are able to return to work within 2 weeks of surgery.

Your surgeon will be able to give you more advice about your recovery.

Causes of pilonidal sinus

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.

This may either be hair growing around the buttock area, or loose hair shed from the buttocks or elsewhere that gathers around the buttock cleft and enters the pilonidal sinus.

Pilonidal sinuses are more common in men because they tend to be hairier.

Sitting for long periods can also increase your chances of getting a pilonidal sinus.

Page last reviewed: 11 December 2020
Next review due: 11 December 2023