What is pilonidal disease?

Pilonidal disease is a condition that affects your skin, usually in the crease between your buttocks.

If you have pilonidal disease, you may have one or more of the following:

• a pilonidal sinus — narrow tunnels (tracts) under your skin
• a pilonidal cyst — a non-inflamed lump filled with fluid

The sinuses or cysts contain hair and may become swollen or infected, which is called an abscess.

What are the symptoms of pilonidal disease?

You may not have any symptoms unless a sinus or cyst becomes infected.

If the pilonidal cyst is infected and turns into an abscess, it can be very painful. Other signs of infection include:

• redness or swelling
• pain, especially when you sit
• pus or blood coming from the abscess (you may notice staining in your underwear)
• an unpleasant smell
• fever

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What causes pilonidal disease?

The cause of pilonidal disease is not fully understood.

Hair often grows in the crease between the buttocks. These hairs can push into your skin, leading to irritation and swelling (inflammation).

Pilonidal disease is more common in:

• males
• people between 15 and 25 years of age
• people with a lot of body hair
• people who sit for long periods
• people with a family history of pilonidal disease

A pilonidal cyst is a sac filled with fluid that forms at the top of the crease between your buttocks. It may have a hair sticking out and can become infected and painful.

When should I see my doctor?

See your doctor if you notice a small lump at the top of your bottom (between your buttocks) that is:

• painful
• red
• warm or hot to touch
• swollen
• bleeding
• leaking pus or fluid

These signs may mean the lump is infected. Infections can develop quickly over a few days and should be treated by a doctor.

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How is pilonidal disease diagnosed?

Your doctor will ask you about your symptoms and look at the affected area.

You usually won't need blood tests or imaging scans to diagnose pilonidal disease. The tests might be used if your doctor thinks you may have complications.

If there is pus, your doctor may take a swab to find out which bacteria are causing the infection.

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How is pilonidal disease treated?

If your pilonidal sinus or cysts aren't causing any symptoms, treatment usually starts with hair removal and good hygiene in the area.

If you have an abscess, it's important to have it treated properly to lower your chance of it coming back.

For simple pilonidal abscesses and sinuses, the most common treatment is called deroofing and curettage. This means:

• the top (roof) of the abscess or sinus is removed
• the area is cleaned by scraping out hair, fluid and dead tissue
• the wound is left open to heal and covered with a dressing

It is often done under local anaesthetic, but sometimes general anaesthetic is used. It is important to follow your doctor's wound care instructions closely.

If your pilonidal disease is complicated or keeps coming back, your doctor might suggest a more complex type of surgery. These surgeries involve removing or cleaning out all the sinus tracts. After the surgery:

• the wound may be left open to heal and covered with a dressing
• the wound may be closed with sutures
• it may take 2 to 3 weeks before you're ready to go back to work, depending on the type of surgery

Antibiotics may be prescribed if the skin around the abscess or sinus is infected (this is called cellulitis).

What are the complications of pilonidal disease?

Complications are often related to wound healing and may include:

• infection in the wound
• a collection of blood under the skin like a large bruise (called a haematoma)
• a pocket of clear fluid under the skin (called a seroma)
• the wound opening again before it has fully healed

The abscess or sinus can be bigger than it looks from the outside. This means surgery may need to be more complex than planned, which may raise the chance of complications.

Pilonidal disease may also come back after treatment.

Can pilonidal disease be prevented?

Pilonidal disease can't always be prevented because the cause is not fully known.

You can help lower your chance of it coming back by looking after the area carefully. Here are some things that may help:

• Keeping the area clean and dry.
• Wash the area with antibacterial soap.
• Make sure all soap is rinsed off after cleaning.
• Avoid long periods of sitting — take regular breaks to stand and move around.
• Consider laser hair removal. Talk to your doctor about laser hair removal to reduce hair growth in the area.

Resources and support

International Pilonidal Society is an Australian-founded organisation that can help you find surgeons with an interest in pilonidal sinus.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.