A pilonidal cyst is a fluid-filled developmental defect at the base of the spine.

The terms cyst, sinus, and abscess refer to different stages of the disease process.

  • Cyst—not infected
  • Abscess—pocket of pus
  • Sinus—opening between a cyst or other internal structure and the outside

While the cyst is not serious, it can become infected and may need to be treated if problems develop. When a pilonidal cyst gets infected, it forms an abscess, eventually draining pus through a sinus.

Pilonidal Cysts

Pilonidal cyst
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A pilonidal cyst may be congenital or acquired. If congenital, it probably began as a defect that existed when you were born. Sometime later, the defect allowed an infection to develop. If acquired, it may be the enlargement of a simple hair follicle infection or the result of a hair penetrating the skin and causing an infection.

Risk Factors

The following factors increase your chance of developing a pilonidal cyst:

  • Personal or family history of similar problems such as acne boils, carbuncles, folliculitis, and sebaceous cysts
  • Large amounts of hair in the region
  • Tailbone injury
  • Horseback riding, cycling
  • Prolonged sitting
  • Obesity


A pilonidal cyst may cause:

  • Painful swelling over your sacrum, which is the area just above your tailbone
  • A foul smell or pus draining from that area


You will be asked about your symptoms and medical history. A physical exam will be done. You may be referred to a surgeon for treatment. There are no diagnostic tests required.


Talk with your doctor about the best treatment plan for you. The choice of treatment will depend on the extent of the condition and your general overall health. Treatment options include:

Home Treatment

As with all localized infections under the skin, warm water soaks will draw out the infection. This will not completely cure the condition, but it will help.

Incision and Drainage

The abscess is lanced, the pus drained, and the wound is packed with sterile gauze. This helps it heal from the inside out. But, this usually does not cure the problem because abnormal tissue remains.


To completely cure the condition, all affected tissue needs to be removed. It may be considered if you have repeated infections. This is a more extensive surgical procedure than simple incision and drainage. The surgical wound may be closed with sutures or left open to heal from the inside.

Laser Hair Removal

There are recent reports that laser hair removal in the area may be an effective treatment for pilonidal cysts.


To help reduce your chance of a pilonidal abscess:

  • Keep the area clean and dry
  • Avoid sitting for a long time on hard surfaces
  • Remove hair from the area