A pilonidal sinus is a small tunnel or tract that forms in the skin at the top of the buttock crease, near the tailbone. It develops when loose hairs get pushed beneath the skin’s surface, triggering inflammation and creating a cavity that can fill with fluid, hair, and debris. The condition affects roughly 40 out of every 100,000 people per year, most commonly between the ages of 15 and 30, and is two to four times more common in men than women.
What Happens Inside the Skin
The crease between your buttocks (called the natal cleft) creates a warm, moist environment where friction is constant. Every time you sit down or stand up, the motion of your buttocks can push loose hairs into the skin. Once a hair penetrates below the surface, your body treats it as a foreign object. Inflammatory tissue forms around the hair, and over time a small tunnel develops in the lower layers of the skin and the fat beneath it.
Inside the tract, you’ll typically find one or more hair shafts surrounded by inflamed tissue. In about half of cases, the tunnel becomes partially lined with skin cells, making it a more permanent structure. The deeper end of the tract often expands into a pocket that can become a chronic abscess cavity. Scar tissue builds up in the walls over time, which is part of why the problem tends to come back even after treatment.
Though the tailbone area is by far the most common site, pilonidal sinuses can also develop between the fingers (especially in barbers who handle cut hair all day), in the belly button, or in the armpit.
Who Gets Pilonidal Disease
The peak age for diagnosis is around 20 in men and 18 in women. A Danish population study found that 20-year-old men had an incidence of roughly 216 per 100,000, while 18-year-old women peaked at about 108 per 100,000. The condition becomes much less common after age 30, likely because hair growth patterns change and the natal cleft tends to become less deep with age.
Several factors increase your risk:
- Excess body hair: More loose hairs in the area means more material to penetrate the skin.
- Sedentary work or prolonged sitting: Driving for long periods is a well-documented risk factor. A study of Turkish soldiers found an 8.8% incidence rate, with vehicle driving as a significant contributor.
- Obesity: A deeper natal cleft and more friction increase the likelihood of hair becoming embedded.
- Family history: The condition runs in families, suggesting that cleft depth, hair type, and skin characteristics play a genetic role.
- Sweating and poor hygiene: Moisture softens the skin, making it easier for hair to push through.
What It Feels Like
Many pilonidal sinuses start with no symptoms at all. You might notice a small dimple or pit at the top of your buttock crease and nothing else. The first real symptom is usually pain when sitting. From there, the condition can follow a few different paths.
In a mild or chronic case, you may notice a small lump that occasionally leaks fluid or blood. It might be tender when you press on it, but manageable day to day. Some people live with this for months or years, with symptoms that come and go.
When the sinus becomes infected and forms an abscess, things escalate quickly. The area turns red, swollen, and intensely painful. Foul-smelling pus may drain from the opening. In severe infections, you can develop a fever, nausea, and exhaustion. It’s also possible to develop more than one abscess at the same time. An acute abscess usually needs to be drained before any further treatment.
How It’s Treated
Treatment depends on whether you’re dealing with a one-time abscess, a chronic sinus that keeps flaring up, or a first episode that hasn’t gotten too complicated.
For an acute abscess, the first step is drainage. This is a relatively quick procedure, often done under local anesthesia, that provides fast pain relief. But drainage alone doesn’t remove the sinus tract itself, so the problem frequently returns.
For chronic or recurrent disease, surgery is the standard approach. The main options differ in how the wound is handled afterward. In open excision, the sinus is cut out and the wound is left open to heal from the bottom up. This takes about 6 to 8 weeks to fully close. Most people take 7 to 10 days off work, though activities like cycling are off limits for 6 to 8 weeks.
Flap-based techniques, such as the Limberg flap or Karydakis procedure, involve removing the sinus and then shifting nearby skin to cover the wound. These methods have lower recurrence rates than simple excision with primary closure, and they allow a faster return to normal life, though recovery still requires at least two weeks off work. Primary closure, where the wound is simply stitched shut after excision, has a significantly higher recurrence rate compared to other methods.
Newer minimally invasive options include laser treatment, where a fiber is inserted into the sinus to destroy the tract from the inside. Recovery is faster, but the long-term results are still being compared against traditional surgery. Studies show recurrence rates for laser treatment are roughly similar to other non-surgical approaches like chemical treatments at the one and two-year marks.
Preventing Recurrence
Pilonidal disease has a frustrating tendency to come back regardless of how it’s treated. One of the most effective prevention strategies is keeping the area free of hair. A clinical trial at Nationwide Children’s Hospital enrolled 302 patients aged 11 to 21 and found that laser hair removal, combined with standard wound care, cut the one-year recurrence rate from 33.6% to 10.4%. That’s a substantial difference with no increase in complications or recovery time.
Beyond hair removal, practical steps include keeping the natal cleft clean and dry, avoiding prolonged sitting when possible (or taking regular breaks if you drive for work), and maintaining a healthy weight. Some surgeons recommend regular shaving or depilatory creams around the surgical site if laser hair removal isn’t accessible, though these are less effective and require ongoing commitment.