Pilonidal Sinus

What Is Pilonidal Sinus Disease (PNS)?

A pilonidal sinus (PNS) is a small cyst or abscess that occurs in the cleft at the top of the buttocks. A PNS usually contains hair, dirt, and debris. It can cause severe pain and can often become infected. If it becomes infected, it may ooze pus and blood and have a foul odor.

A PNS is a condition that mostly affects men and is also common in young adults. It’s also more common in people who sit a lot, like cab drivers.

What Are the Causes of Pilonidal Sinus Disease?

The exact cause of this condition is not known, but its cause is believed to be a combination of changing hormones (because it occurs after puberty), hair growth, and friction from clothes or from spending a long time sitting.

Activities that cause friction, like sitting, can force the hair growing in the area to burrow back under the skin. The body considers this hair foreign and launches an immune response against it, similar to how it would react when dealing with a splinter. This immune response forms the cyst around your hair.

Identifying a Pilonidal Sinus and Recognizing Signs of Infection

You may not have any noticeable symptoms at first other than a small, dimple-like depression on the surface of your skin. However, once the depression becomes infected, it will quickly develop into a cyst (a closed sac filled with fluid) or an abscess (a swollen and inflamed tissue where pus collects).

The signs of an infection include:

  • pain when sitting or standing
  • swelling of the cyst
  • reddened, sore skin around the area
  • pus or blood draining from the abscess, causing a foul odor
  • hair protruding from the lesion
  • formation of more than one sinus tract, or holes in the skin

You may also experience a low-grade fever, but this is much less common.

How Are Pilonidal Sinuses Treated?

Conservative Treatment

If your case is diagnosed early on, you aren’t experiencing severe pain, and there’s no sign of inflammation, it’s likely that your doctor will prescribe a broad-spectrum antibiotic, which is an antibiotic that treats a wide range of bacteria. It’s important to realize that this won’t heal the sinus tract, but it will give you relief from the infection and discomfort. Your doctor will recommend that you get a follow-up exam, regularly remove hair or shave the site, and pay particular attention to hygiene.


Before this procedure, your doctor will give you a local anesthetic. They will then use a scalpel to open the abscess. They will clean away any hair, blood, and pus from inside the abscess.

Your doctor will pack the wound with sterile dressing and allow it to heal from the inside out. The wound usually heals within four weeks, and many patients don’t require any further treatment.

Phenol Injection

For this type of treatment, your doctor will first give you a local anesthetic. They will then inject phenol, a chemical compound used as an antiseptic, into the cyst. This procedure may need to be repeated several times. Eventually, this treatment will cause the lesion to harden and close.

This treatment has a very high recurrence rate. Therefore, it’s very uncommon in the United States. Doctors turn to surgery as the treatment of choice in some cases.


If you have a recurring PNS or if you have more than one sinus tract, your doctor will recommend a surgical procedure.

You will first be given a local anesthetic. Then, the surgeon will open the lesions, removing all of the pus and debris. Once this process is complete, the surgeon will stitch the wounds closed.

After surgery, your doctor will explain how to change the dressings and will recommend shaving the site to prevent hair from growing into the wound.

What Is the Outlook for Pilonidal Sinus Disease?

Depending on the severity of the disorder and the type of treatment, a PNS will usually clear up within four to 10 weeks.

What Complications Are Associated With Pilonidal Sinus Disease?

There are a number of complications that may arise from PNS. These include wound infection and a recurrence of the PNS even after surgery.

Signs that the wound is infected include:

  • severe pain
  • inflamed, swollen skin
  • a temperature of 100.4°F or higher
  • blood and pus seeping from the wound site
  • a foul odor coming from the wound

How Can I Prevent Pilonidal Sinus Disease?

You can prevent recurrence of PNS by washing the area on a daily basis with a mild soap, making sure all soap is removed, keeping the area completely dry, and avoiding sitting for long periods.

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