Pilonidal Sinus (Pilonidal Cyst)
A small pit or tunnel in the skin at the top of the buttock crease, where loose hairs get pushed in and set up inflammation. Many cause no trouble at all. When one gets infected it becomes a painful swelling that can leak pus and make sitting miserable.
Quick answer: A pilonidal sinus (or cyst) is a small pit or tunnel at the top of the buttock crease, caused by hairs working into the skin. If it causes no symptoms, it can be left alone. A painful, infected lump usually needs draining. Sinuses that keep flaring are removed surgically, and hair removal helps stop them coming back.
Who gets it. Mostly young people from puberty to about 40, and men much more often than women. It’s more likely with more body hair, a deep buttock crease, long hours sitting, sweating and extra weight. It was nicknamed ‘jeep disease’ in the Second World War because so many soldiers riding in jeeps got it.
Causes. Loose hairs are drilled into the skin of the crease by friction and pressure. The body treats them as a foreign body, forming a pit, then a tunnel, which can become infected.
Symptoms. Tiny pits in the midline of the crease, sometimes with hairs poking out. When infected: pain, swelling and redness at the top of the crease over a few days, and pus or blood leaking. Repeated infections can leave a tract that keeps weeping.
Look-alikes. Boils, hidradenitis suppurativa (lumps in other skin folds too), an anal fistula (an opening nearer the anus, so your doctor may examine there), and occasionally Crohn’s disease.
How it’s diagnosed. By looking. Scans are rarely needed.
The pilonidal sinus ladder
No symptoms means no treatment. The aim is to drain infection when it happens, then remove sinuses that keep flaring, with the least time off.
- Step 1 · Self-careKeep the crease clean, dry and hair-freeDaily shower, dry well, loose cotton underwear, breaks from long sitting. Hair removal by clipping, cream or laser.
- Works
- US colorectal surgeons recommend hair removal; evidence is mostly from observational studies. Laser may lower the chance of it coming back after surgery
- Cost
- Free; laser hair removal about $100–300 a session
- How long
- Ongoing, especially after treatment
- Watch for
- Shaving can nick the skin. Ask your GP which method suits you.
Hairs are the culprit. Evict them politely.
- Step 2 · GP or emergencyDraining an abscessA small cut under local anaesthetic to let the pus out, usually the same day, then dressings.
- Works
- Quick relief. About 6 in 10 first abscesses heal with drainage alone, but up to 4 in 10 come back
- Cost
- Usually Medicare-covered at a GP or public hospital
- How long
- Heals over 2–4 weeks
- Watch for
- Antibiotics alone don’t clear an abscess. They’re only added for spreading redness or other health problems.
Pus needs a door, not a pep talk.
- Step 3 · SpecialistMinimally invasive options (pit-picking, phenol, endoscopic or laser treatment)The pits and tract are cleaned out through tiny openings without a big wound.
- Works
- Phenol clears the problem in at least 2 in 3 people in studies, with a quicker return to normal life than open surgery
- Cost
- Public waiting lists; private fees vary
- How long
- Back to normal in days to a few weeks
- Watch for
- May need repeating, and the chance of it coming back can be higher than with excision.
Small cuts, small recovery, slightly bigger maybe.
- Step 4 · SpecialistExcision surgery (open healing or off-midline closure)The sinus is cut out. The wound is left open to heal from the base, or closed with stitches, ideally to one side of the crease (for example a cleft lift or flap).
- Works
- In a Cochrane review, open wounds came back less often than closed ones but took longer to heal. If closed, off-midline beats midline: midline closures had over 4 times the odds of coming back
- Cost
- Public waiting lists; private fees vary
- How long
- Open wounds can take weeks to months with dressings; closed wounds about 2 weeks
- Watch for
- Wound infection and slow healing. Ask your surgeon which method they recommend and why.
The right wound in the right place beats the fastest one.
Save your money
Popular, heavily marketed or often asked about, but the evidence is weak or says no.
- Squeezing or popping itPushes infection deeper and doesn’t remove the hairs or tract.
- Antibiotics instead of draining an abscessAntibiotics can’t get into a pocket of pus. Drainage is the treatment; antibiotics are only for spreading infection.
What you can do
- Shower daily and dry the crease thoroughly.
- Take a break from sitting at least every hour on long drives, desk days or gaming sessions.
- Keep the area hair-free once it has settled, especially after treatment.
- Use paracetamol or ibuprofen for pain while waiting to be seen.
- After surgery, follow the dressing plan and keep hair away from the wound.
See your GP if
- You have a painful lump at the top of your buttock crease, especially if it’s leaking pus or blood (ask for an urgent appointment)
- A pit or tract keeps weeping
- It keeps flaring up after being drained
See a doctor the same day for a fast-growing, very painful swelling, spreading redness, fever or feeling unwell, especially if you have diabetes or a weakened immune system.
Outlook. Many people have one or two flares and nothing more, and it becomes uncommon after 40. It does tend to come back, especially after simple drainage, so if you’ve had several flares, ask about a definitive treatment.
Common questions
Will a pilonidal cyst go away on its own?
A pit that causes no symptoms can be left alone, and many never cause trouble. An infected, painful lump rarely settles properly on its own and usually needs draining.
Should I squeeze a pilonidal cyst?
No. Squeezing pushes infection deeper and leaves the hairs and tunnel behind. See your GP for a painful or leaking lump.
What causes a pilonidal sinus?
Loose hairs pushed into the skin of the buttock crease by friction and pressure. The body reacts to them, forming a pit and tunnel that can get infected. Long sitting, more body hair and a deep crease make it more likely.
Do I need antibiotics for a pilonidal abscess?
Usually not. The pus needs draining. Antibiotics are added only if redness is spreading, you’re unwell, or you have diabetes or a weak immune system.
How long does pilonidal surgery take to heal?
With stitches, most people are back at work in about 2 weeks. A wound left open to heal can take weeks to a few months of dressings. Minimally invasive treatments usually heal in a few weeks.
Can a pilonidal sinus come back after surgery?
Yes, it can. Open healing and off-midline closure have lower recurrence than a stitched midline wound. Keeping the area hair-free afterwards helps.
Evidence and more information
- NHS: Pilonidal sinus
- Am Fam Physician 2019: Pilonidal disease management, guidelines from the American Society of Colon and Rectal Surgeons
- Al-Khamis et al, Cochrane 2010: Healing by primary versus secondary intention after surgery for pilonidal sinus
- healthdirect: Surgery for pilonidal sinus
maladywise.com/pilonidal-sinus/