Back

Pilonidal Cyst

What Is It, Causes, Treatment, and More

Author:Ali Syed, PharmD

Editors:Alyssa Haag,Ian Mannarino, MD

Illustrator:Jessica Reynolds, MS

Copyeditor:David G. Walker


What is a pilonidal cyst?

A pilonidal cyst, also known as pilonidal disease or pilonidal sinus, is a skin condition characterized by the presence of an abnormal sac-like structure in the skin filled with hair, fluid, and skin debris. A pilonidal cyst typically appears in the tailbone area, usually in the crease of the buttocks or in the cleft on top of the buttocks. Pilonidal cysts are quite common with more than 70, 000 cases reported in the U.S. annually.

What causes a pilonidal cyst?

The exact cause behind the formation of a pilonidal cyst is not completely understood and is likely multifactorial. Pilonidal cysts are commonly caused by ingrown hairs, which result when hairs grow in the crease of the buttocks and burrow under the skin. Formation of an ingrown hair may lead to an immune response, thereby resulting in cyst formation. Loose hairs may also become trapped in the crease of the buttocks, which occurs more commonly in individuals who have coarse or stiff body hair that is likely to puncture the skin.

Certain factors that can stimulate the formation of ingrown hairs include sitting or exercising for prolonged periods of time; wearing tight clothing; obesity; and anything that may increase friction, sweat, and heat in the buttocks area. These situations may also irritate hair follicles, which can become blocked with dead skin cells and bacteria, leading to cyst formation.

Young males are at higher risk of developing a pilonidal cyst. They typically develop after puberty due to changes in hormones and increased hair growth during this period, but they may develop until the age of 40. Pilonidal cysts may also be congenital and appear at birth. Other risk factors for developing a pilonidal cyst include an inactive lifestyle, previous occurence of pilonidal cysts, or having a family history of pilonidal cysts. If a pilonidal cyst becomes infected due to lack of treatment, painful skin abscess or sinus tracts, which are empty spaces underneath the skin, may develop. If a chronically infected pilonidal cyst is not treated appropriately, the individual may be at a higher risk of developing a skin cancer known as squamous cell carcinoma.

Excited Mo character in scrubs
Join millions of students and clinicians who learn by Osmosis!
Start Your Free Trial

What are the signs and symptoms of a pilonidal cyst?

The most common signs and symptoms of a pilonidal cyst include the presence of a small dimple or irritated mass in the buttock area, typically characterized by inflammation, redness, swelling, tenderness, and pain that worsens when walking or sitting. An infected pilonidal cyst may drain pus or blood and can be foul smelling. Some individuals with an infected pilonidal cyst may experience nausea, fever, or extreme fatigue; but these symptoms are less common.

How is a pilonidal cyst diagnosed?

A pilonidal cyst must be diagnosed by a medical professional after a thorough review of symptoms and medical history and after conducting a physical examination. A pilonidal cyst is most commonly diagnosed upon visual inspection of the buttock area by a medical professional. In rare cases where infection is suspected, blood tests, urine samples and fluid samples from the pilonidal cyst may be assessed. In certain cases, imaging in the form of an X-ray, CT, or MRI may be ordered to explore sinus cavities, infection spread, or the depth of the cyst. If any type of skin cancer is suspected, biopsies of the skin may be taken as well. 

How is a pilonidal cyst treated?

Treatment for a pilonidal cyst varies depending on the severity of symptoms and pattern of disease. The most common treatment for a pilonidal cyst is incision and drainage of the cyst in which a small incision is made in the cyst, which releases any fluid, hair, and debris in the cyst and prevents infection. If infection has already occurred or is suspected, incision and drainage is useful in draining pus and may be followed by a course of oral and/or topical antibiotics. Incision and drainage of a pilonidal cyst may result in chronic pilonidal cysts, which are prone to repeated infections. In severe cases with high recurrence of infection, limited healing, or the presence of multiple openings in the cyst, surgery may be required to fully remove it; this may decrease the rate of recurrence. After surgery, the wound may be left open and packed with dressing or may be closed with stitches. It must remain clean, dry, and free of hair until fully healed.

In very mild cases, oral antibiotics such as cephalexin or sulfamethoxazole-trimethoprim and/or topical antibiotics, such as fucithalmic acid, may be prescribed with close monitoring of the cyst. However, while antibiotics may aid in relieving inflammation, they may not completely treat pilonidal cysts. Less common treatments include the use of localized injections of acidic chemical compounds, such as phenol, to treat and prevent mild-to-moderate pilonidal cysts. This method, however, is associated with a high recurrence rate and is not commonly used. 

During treatment, hot water soaks or sitz baths may be used to provide symptomatic relief. Non-prescription pain relieving medications, such as acetaminophen or ibuprofen, may also be used. It is important to keep the affected area clean, dry, and free of hair if possible. 

Formation of a pilonidal cyst can be prevented through hair removal in the tailbone area and crease of the buttocks by shaving, using hair removal cream, or undergoing laser hair removal. Additional prevention methods include avoiding tight clothes, sitting and exercising for shorter periods of time, sitting on soft surfaces, practicing good posture and hygiene, and regularly exfoliating the area. 

Can a pilonidal cyst go away on its own?

A pilonidal cyst can drain and resolve on its own. In individuals with chronic pilonidal cysts, symptoms may appear and disappear over time. 

What are the most important facts to know about a pilonidal cyst?

A pilonidal cyst is a skin condition characterized by the presence of an abnormal sac-like structure in the skin, typically in the crease of the buttocks and filled with hair, fluid, and skin debris. Pilonidal cysts are commonly caused by ingrown hairs, which result when hairs grow in the crease of the buttocks and burrow under the skin. The most common signs and symptoms of a pilonidal cyst include the presence of an irritated mass characterized by inflammation, redness, swelling, tenderness, and pain that worsens when walking or sitting. An infected pilonidal cyst may drain pus or blood, which may be foul smelling. A pilonidal cyst is most commonly diagnosed on visual inspection of the buttock area, alongside blood tests, urine samples, fluid samples and imaging as needed. The most common treatment for a pilonidal cyst is incision and drainage of the cyst with or without a course of oral and/or topical antibiotics as appropriate. In severe cases, surgery may be required to fully remove the pilonidal cyst, which may decrease the rate of recurrence. A pilonidal cyst can drain and go away on its own; however, in individuals with chronic pilonidal cysts, symptoms may appear and disappear over time. 

Quiz yourself on Pilonidal Cyst

31 Questions available

Quiz now!

Watch related videos:

Mo with coat and stethoscope

Want to Join Osmosis?

Join millions of students and clinicians who learn by Osmosis!

Start Your Free Trial

Related links

Skin and soft tissue infections: Clinical practice
Autoimmune bullous skin disorders: Clinical practice
Skin cancer
Skin anatomy and physiology
Acneiform skin disorders: Pathology review

Resources for research and reference

Healthwise Staff. (2020). Pilonidal Disease. In HealthLink BC. Retrieved Oct 26, 2021, from https://www.healthlinkbc.ca/health-topics/ug1160

Hyppolito da Silva, J. (2000). Pilonidal cyst. Diseases of the Colon & Rectum, 43(8), 1146-1156. DOI: 10.1007/BF02236564 

Lee, H., Jehan, F., Gachabayov, M., Alizadeh, K., & Bergamaschi, R. (2021). Squamous cell carcinoma in untreated pilonidal cyst. Techniques in Coloproctology, 25(2), 241-243. DOI: 10.1007/s10151-020-02298-3

Pilonidal Cyst. (2020). In Cleveland Clinic. Retrieved Oct 26, 2021, from https://my.clevelandclinic.org/health/diseases/15400-pilonidal-disease

Pilonidal Cyst. (2018). In The University of Texas at Austin-University Health Services. Retrieved Oct 26, 2021, from https://www.healthyhorns.utexas.edu/HT/HT_pilonidalcyst.html

Pilonidal Cyst. (2021). In UVA Health. Retrieved Oct 25, 2021, from https://uvahealth.com/services/dermatology/pilonidal-cyst

Pilonidal Disease. (2020) In American Society of Colon and Rectal Surgeons. Retrieved Oct 25, 2021, from https://fascrs.org/patients/diseases-and-conditions/a-z/pilonidal-disease