Pilonidal sinus

A pilonidal sinus is a small hole or tunnel at the top of your bottom, between your buttocks. Treatment is usually only needed 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 at the top of the cleft in your buttocks, and a pus-filled skin abscess can develop.

Sometimes a pus-filled abscess can develop suddenly, causing pain and swelling, and making it difficult to sit down.

If you keep getting infections you may have ongoing problems, like discomfort or pain, and regularly seeping pus or blood.

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

Urgent advice: Ask for an urgent GP appointment or contact NHS 111 if:

  • you have a small lump at the top of your bottom (between your buttocks) that's painful, 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 for a pilonidal sinus 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:

If you have a painful, swollen abscess, it usually needs to be cut and the pus drained. You may also need antibiotics.

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 non-steroidal anti-inflammatory drugs (NSAIDs), to help reduce pain and swelling.

Incision and drainage

This is a procedure for an infected abscess.

A small cut (hole) is made in the abscess so the pus can be drained. This is usually arranged on the same day as you see your GP.

Wide excision and open healing

You may need 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

This surgery is for a large or repeatedly infected pilonidal sinus.

The sinus is removed and an oval-shaped flap of skin cut out on either side of it. The 2 sides are then stitched together.

Endoscopic ablation for a pilonidal sinus

This procedure is to clean a pilonidal sinus and encourage healing.

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 is cleaned with a special solution. Heat is used to seal the sinus.

Other treatments

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 to close the sinus, like injection with fibrin glue, may be available in some places.


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

Your care team will advise you about how to care for your wound while it heals and what to do if symptoms come back.

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

Going back to work

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: 16 November 2023
Next review due: 16 November 2026