A pilonidal cyst typically appears as a small dimple, pit, or swollen lump at the top of the buttock crease, right at the base of the tailbone. In its earliest form it can be easy to miss, looking like nothing more than a tiny hole in the skin. Once inflamed or infected, it becomes an unmistakable red, tender bump that can grow to several centimeters across. What it looks like depends heavily on what stage it’s in.
Where It Forms and Why
Pilonidal cysts sit in the cleft between the buttocks, in the narrow strip of skin overlying the sacrum and coccyx. They develop when loose hairs work their way into the skin, triggering the body’s immune response to a foreign object. After puberty, hormonal changes cause hair follicles in this area to produce more keratin, which can clog and distend the follicle. The blocked follicle eventually ruptures beneath the skin’s surface, creating an abscess and then a tunnel (called a sinus tract) that connects a deep pocket under the skin to the opening on the surface.
The condition is most common in young adults. Danish population data shows the highest rates occur in men around age 20 and women around age 18. Overall incidence has been climbing, rising from about 26 to nearly 40 cases per 100,000 people over the past two decades. Having a family history of pilonidal disease increases both your risk and the chance of recurrence after treatment.
The Earliest Stage: Midline Pits
Before any symptoms develop, a pilonidal cyst often looks like one or more tiny pits or holes along the midline of the gluteal cleft. These openings can be so small you might only notice them if you’re looking closely in a mirror or someone else points them out. A single pit is the most common presentation, though some people develop a cluster of two or three. You may see a fine hair poking out of the opening.
At this stage the surrounding skin looks completely normal. There’s no redness, no swelling, and no pain. Many people live with these pits for years without ever knowing they’re there, and some never progress beyond this stage.
What an Inflamed Cyst Looks Like
When the cyst becomes irritated or mildly infected, the skin around the pit turns red and puffy. You’ll notice a firm, dome-shaped lump just above or slightly to one side of the tailbone, often tender to the touch. The surrounding skin feels warm. At this point the bump may be the size of a marble or a small grape, and sitting or leaning back becomes uncomfortable.
If the infection worsens into a full abscess, the lump grows larger, and the redness spreads outward in a halo. The swelling can make it look like a boil. Pressure builds inside, and you may see the skin become taut and shiny over the most swollen point. Some abscesses develop a visible white or yellowish head where pus is close to the surface.
Drainage: What Comes Out
A pilonidal cyst that has opened or ruptured on its own will leak fluid. That drainage can range from clear or blood-tinged to thick, yellowish, or greenish pus. Infected drainage often has a noticeably foul smell. You might also see small tufts of hair mixed in with the discharge, which is a hallmark of pilonidal disease specifically. The drainage can stain clothing and may be persistent, leaving the area damp between episodes.
Chronic or Recurring Disease
Pilonidal cysts that come back repeatedly or never fully resolve take on a different appearance. Chronic disease creates visible, slightly raised tracts under the skin, typically 2 to 5 centimeters long, running upward from the original pit toward the lower back. The skin over these tracts can look dimpled, scarred, or discolored compared to the surrounding area. Multiple pit openings may develop along the tract line.
Inside, these tracts are lined with skin cells and lead to a deeper pocket filled with granulation tissue (the body’s wound-repair material) and tangled nests of loose hair. In about 90% of cases, the tract angles upward toward the lower back, placing the deeper end roughly 5 to 8 centimeters from the anus. The chronic cycle of flare-ups, drainage, and partial healing leaves the tissue progressively more scarred with each episode.
What It Looks Like After Surgery
The post-surgical appearance depends on which procedure was performed. After a simple drainage, you’ll have a small incision that’s typically left open to heal from the inside out. The wound is packed with gauze initially, and over weeks it gradually fills in with new tissue, shrinking from the edges inward.
More extensive operations that involve cutting away the entire cyst and surrounding tissue can leave larger wounds. When surgeons close the wound with a flap technique (rotating nearby skin to fill the gap), the result is a sutured line that may cross the midline of the cleft. This can leave a visible scar and sometimes creates a slight asymmetry in the contour of the buttocks. When larger wounds are left open to heal on their own, the recovery is more demanding. Healing can take over six months, and the wound goes through stages: initially a deep, open cavity that slowly fills with pink granulation tissue before the skin edges finally close over it.
Recurrence rates vary by treatment. Flap-based procedures have the lowest reported recurrence, ranging from 0% to 6%. Primary closure (stitching the wound shut directly) can achieve similarly low rates in experienced hands, though results vary. Less invasive options like chemical treatments applied to the tract eliminate recurrence in roughly 80% or more of patients, with rates of return between 0% and 19% depending on the study and follow-up period.
How to Tell It Apart From Other Conditions
Several other skin problems can appear near the tailbone, so location and specific features matter. A boil or skin abscess can look nearly identical when inflamed, but it won’t have a midline pit with hair visible in the opening. A perianal abscess forms closer to the anus and is associated with different symptoms. A dermoid cyst is present from birth and tends to sit deeper, without a surface pit.
The key visual markers of a pilonidal cyst are its position right in the gluteal cleft at the level of the tailbone, the presence of one or more midline pits, and the appearance of hair in or around the opening. If you can see a small hole in the crease between the buttocks with redness or swelling around it, especially if there’s any drainage, that combination is highly characteristic of pilonidal disease.