What Is a Pilonidal Sinus?

The exact cause of an infected pilonidal sinus isn’t known, but it’s 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. Sometimes a person may have multiple sinuses that connect under the skin.

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.

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. A broad-spectrum antibiotic 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.

Lancing

This procedure alleviates symptoms from an abscess, or a collection of pus inside the sinus. 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 people 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 uncommon in the United States. Doctors turn to surgery as the treatment of choice in some cases.

Surgery

If you have a recurring pilonidal sinus infection 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.

Depending on the severity of the disorder and the type of treatment, an infected pilonidal sinus will usually clear up within 4 to 10 weeks.

There are a number of complications that may arise from pilonidal sinus infection. These include wound infection and a recurrence of the infection 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

You can prevent a pilonidal sinus infection 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