Skin Health More Skin Conditions What Is an Epidermoid Cyst? By Heather L. Brannon, MD Heather L. Brannon, MD Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years. Learn about our editorial process Updated on May 28, 2023 Medically reviewed by Casey Gallagher, MD Medically reviewed by Casey Gallagher, MD Casey Gallagher, MD, is board-certified in dermatology and works as a practicing dermatologist and clinical professor. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Symptoms Causes Diagnosis Treatment Epidermoid cysts are non-cancerous, balloon-like bumps that slowly develop under the skin. They are filled with a substance called keratin and can range in size from less than one-quarter of an inch to several inches wide. The cysts can sometimes rupture and drain a thick, yellow, foul-smelling fluid. Epidermoid cysts can appear anywhere but are most often seen on the face, scalp, trunk, groin, and upper back. Though typically harmless, the cysts may require treatment if they become enlarged or infected. This article describes the symptoms and causes of epidermoid cysts as well as how they are diagnosed, treated, and prevented. Also Known As Epidermal cystEpidermoid inclusion cystEpithelial cystFollicular infundibular cystInfundibular cystKeratin cyst Verywell / Brianna Gilmartin What Are the Symptoms of Epidermoid Cysts? An epidermoid cyst looks like a raised, round bump. Like all cysts, it is filled with fluid. With an epidermoid cyst, you can usually feel the cyst wall and move the cyst around fairly easily under the skin. There may also be a small, pore-like opening on the surface of the skin. Other symptoms of an epidermoid cyst include: Pain and pressure under the skinTenderness when touchedRedness and swellingA yellowish, thick discharge with a foul odor DermNet / CC BY-NC-ND When to See a Healthcare Provider Epidermoid cysts usually don't cause any problems, but you should see a healthcare provider if it is: Fast-growingVery largePainful, red, and hotLeaking fluid If the cyst wall ruptures, it can lead to an infection. What Are the Symptoms of an Infection? What Causes Epidermoid Cysts? Epidermoid cysts are the most common type of skin cyst. They occur when epidermal cells—those that make up the outermost layer of skin called the epidermis—don't shed properly and move beneath the skin's surface. Epidermal cells produce a type of protein called keratin that makes up your skin, hair, and nails. When these cells are trapped beneath the skin, they will continue to produce keratin, leading to the formation of a fully contained, fluid-filled cyst. The entrapment of epidermal cells may be caused by an injury, surgery, or body piercing. some occur spontaneously for no known reason. On rare occasions, they can occur with genetic disorders like pachyonychia congenita. Epidermoid Cyst vs. Dermoid Cyst Epidermoid and dermoid cysts are similar in that they both contain keratin. But a dermoid cyst tends to develop when a hair follicle is blocked. Dermoid cysts are also usually deeper and often contain a skin oil called sebum produced by the sebaceous glands. Layers of Skin and Their Functions How Are Epidermoid Cysts Diagnosed? Epidermoid cysts account for the majority of cysts seen by dermatologists, so they can often be diagnosed by their appearance alone. If needed, an ultrasound (which produces images using sound waves) can help visualize the structure, position, and size of the cyst. The cyst wall will be clearly seen on an ultrasound, while the center of the cyst will look like ground glass. To confirm the diagnosis, the dermatologist may want to rule out other possible causes in the differential diagnosis, including: Nodular acne: A severe type of acne that causes hard lumps or knots Sebaceous cyst: A type of cyst caused by a plugged sebaceous gland Furuncle: Also known as a boil Lipoma: A harmless fatty tumor located just below the skin Sebaceous hyperplasia: Skin-colored bumps caused by overactive sebaceous glands An in-office biopsy can be performed to obtain a tissue sample for a pathologist to examine under a microscope. When seen up close, the cells will look clumped, fibrous, and horn-like. Boil vs. Cyst: How to Tell the Difference How Are Epidermoid Cysts Treated? An epidermoid cyst doesn't usually have to be treated if small and painless. Even so, some people may want it drained for cosmetic reasons, especially if it is on the face. The draining of a cyst should be done by a healthcare provider under sterile conditions. Afterward, you may be advised to use a warm compress for a few days to help the cyst drain. The warmth can also help promote healing by increasing blood flow to the injury. If the cyst is especially large or inflamed, a corticosteroid (steroid) injection can help reduce swelling and redness. Kenalog (triamcinolone) is commonly used for this. Oral antibiotics may be prescribed if the cyst is infected (or to prevent infection following the cyst drainage). Cortisone Shots for Acne Epidermoid Cyst Removal Your healthcare provider may recommend the removal of an epidermal cyst if it is severe, recurs (comes back), or is located in a place where is continually irritated (such as around the collar or where your glasses touch the skin of your ear). You may also request that a cyst be removed for cosmetic reasons. To remove the cyst, your healthcare provider will first make an incision to extract the keratin content. The cyst wall will then be separated from the surrounding tissues and removed with a pair of forceps or tweezers. If the incision is large, stitches or surgical glue may be needed. By removing the cyst in its entirety, the trapped epidermal cells will no longer produce keratin and the cyst will no longer recur. Can Epidermoid Cysts Be Prevented? Epidermal cysts typically form spontaneously, and there is really no way to prevent them other than to avoid skin injury. With that said, you can prevent scarring and infection by not squeezing, cutting, or popping a cyst. Attempting to remove it yourself increases the likelihood of infection and permanent scarring. Summary An epidermoid cyst is a common, harmless cyst filled with keratin. Small cysts usually don't need to be treated. Sometimes a cyst will grow large and need to be drained. Treatment may also involve antibiotics or a corticosteroid injection. You may want your cyst removed for cosmetic reasons or because it is large and irritating. To remove the cyst, your healthcare provider will first drain it and then remove the cyst wall. Never attempt to remove an epidermoid cyst on your own. 5 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Cedars Sinai. Epidermoid Cysts of the Skin. Wollina U, Langner D, Tchernev G, França K, Lotti T. Epidermoid cysts - a wide spectrum of clinical presentation and successful treatment by surgery: a retrospective 10-year analysis and literature review. Open Access Maced J Med Sci. 2018;6(1):28–30. doi:10.3889/oamjms.2018.027 Hoang VT, Trinh CT, Nguyen CH, Chansomphou V, Chansomphou V, Tran TTT. Overview of epidermoid cyst. Eur J Radiol Open. 2019;6:291–301. doi:10.1016/j.ejro.2019.08.003 Cho Y, Lee DH. Clinical characteristics of idiopathic epidermoid and dermoid cysts of the ear. J Audiol Otol. 2017 Jul;21(2):77-80. doi:10.7874/jao.2017.21.2.77. Kamyab K, Kianfir N, Dasdar Sh, Salehpour Z, Nasimi M. Cutaneous cysts: a clinicopathologic analysis of 2,438 cases. Int J Dermatol. 2020;59(4):457-62. doi:10.1111/ijd.14808 By Heather L. Brannon, MD Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit