What is pilonidal disease?
Pilonidal disease is a chronic infection in the skin slightly above the crease between the buttocks. It develops in a cyst (pilonidal cyst) at the top of or next to the crease between the buttocks (overlying the sacrum). The cyst may look like a small dimple (called a "pit" or "sinus"). Hair may protrude from the pit, and several pits may be seen.
See a picture of a pilonidal cyst.
A pilonidal cyst can be painful enough to make sitting or walking difficult, and in some cases pus or blood may drain from the pit.
What causes a pilonidal cyst?
In the past, most experts believed pilonidal cysts were present at birth (congenital). But now experts think a pilonidal cyst may form in three ways. Some are probably present at birth. But most experts now believe that the cysts develop later in life in one of two ways, or a combination of the two:

• A pilonidal cyst may form when a hair follicle (the sac from which a hair grows) in the skin becomes irritated or stretched. This may be due to exercise that affects the buttocks area (such as horseback riding or cycling), tight clothing around the buttocks, heat, or extensive sweating. The hair follicle becomes blocked and infected and then swells and ruptures into the surrounding tissue, forming an abscess. Continued exercise or walking often pulls hair into the abscess.
• In some people, particularly those with coarse or stiff hair, a loose hair may become trapped in the crease of the buttocks. The hair can poke into the skin, especially if there is already a stretched or irritated hair follicle. Walking and exercise can pull the hair further into the skin. A cyst then forms around the hair and can become infected.

Symptoms
Pilonidal disease is often first recognized as a small dimple (called a "pit" or "sinus") at the top of or next to the crease of the buttocks. Hair may protrude from the pit, and several pits may be seen. Pilonidal disease often has no symptoms. But when infection in the cyst flares up, you may have:

• Discomfort, redness, or swelling at the top of or next to the crease of the buttocks. The cyst can be so uncomfortable that sitting or walking is difficult.
• Cloudy fluid or blood draining from the pits.
• Fever over 100.5°F (38.1°C). But fever is not common.

Although pilonidal disease occurs more in males, it does develop in females. Because of its location, a pilonidal cyst can also cause embarrassment and hinder social interaction. The location of the cyst should not keep you from seeking treatment, though, because help is available.
Because of similar symptoms, a pilonidal cyst is sometimes confused with Crohn's disease or a fistula or abscess next to the rectum.
Exams and Tests
Usually no medical tests are necessary to diagnose pilonidal disease. Your doctor can detect this condition by a visual exam of the area around the crease in the buttocks.
A skin and wound culture of the infected pilonidal cyst (abscess) may be done if it does not heal after treatment.
A pilonidal cyst is sometimes mistaken for Crohn's disease or a fistula or abscess next to the rectum (perirectal abscess). If the doctor suspects another condition, more tests may be done
Treatment Overview
No medical treatment is needed for pilonidal disease that is not causing symptoms. If you have been diagnosed with a pilonidal cyst or pilonidal disease, keep the area around the cyst clean and dry. Use an antibacterial soap to wash the area. And wipe with an alcohol swab 2 to 3 times a day when the pilonidal area begins to get irritated. Your doctor may tell you to keep the area cleared of hair by shaving, using a hair-removing lotion (depilatory), or having electrolysis. This reduces the chance of hair entering the cyst and contributing to infection.
If a pilonidal cyst is infected, your doctor will usually prescribe an antibiotic unless the cyst needs to be drained right away. If antibiotics do not clear up the symptoms, you may need another treatment, such as the following:

• The cyst is cut open and drained (incision and drainage).
• The cyst is removed (excision).

An incision and drainage is sometimes the first option chosen, especially if the cyst is infected. If the pilonidal cyst does not heal, or if it returns, the doctor will perform an excision. To limit the possibility of the infection spreading, incision and drainage may be used instead of excision to reduce the infection. But the treatment chosen depends on how bad the infection is.
Whether you have incision and drainage or excision, it is difficult to heal the wound that is left after the procedure. It is also not uncommon to develop another pilonidal cyst. Be sure to follow your doctor's instructions for caring for the wound and the surrounding skin.
Incision and drainage
During incision and drainage, the hair and pus are removed. The sac that forms the cyst is not removed. The wound is packed with gauze and in general takes at least a month to heal. This procedure can be done in the doctor's office under local anesthesia. The doctor may prescribe antibiotics to help fight the infection.
Excision
In an excision, the infected material is drained and the entire pilonidal cyst is removed. Because an excision is a complex procedure that requires a deeper cut than an incision and drainage, it is usually done at an outpatient surgical center or hospital under general anesthesia.
After the cyst and infected tissue are removed, the wound may be closed with stitches or sutures (closed method) or left open and packed with surgical gauze (open method). If the wound is packed with gauze, the gauze is changed daily until the wound heals.
Excision of the cyst heals within 10 days to 6 weeks or more, depending on the type of surgery.