A skin cyst is a closed pocket of tissue beneath the skin’s surface that fills with fluid, semi-solid material, or other substances. Most skin cysts are benign, grow slowly, and cause no pain unless they become inflamed or infected. They are among the most common reasons people visit a dermatologist or surgeon, yet many people live with them for years without trouble. The term “skin cyst” covers several distinct types, each with its own origin, behavior, and treatment considerations.
How a Skin Cyst Forms
A cyst develops when cells that normally sit on the skin’s surface get pushed deeper into the tissue, where they continue doing what they always do: producing keratin, oil, or other secretions. Because these cells are now trapped beneath the skin, their output has nowhere to go. It accumulates inside a sac lined with the same kind of cells, slowly expanding the pocket over weeks, months, or even years. The result is a firm, round lump you can usually move slightly under the skin with your fingers.
What triggers that initial displacement varies. Damage to a hair follicle from acne, a minor scrape, or even a surgical wound can drive surface cells deeper. Some cysts form around clogged follicle openings. Others arise from developmental quirks present since birth, where tissue that should have stayed on the surface ended up in the wrong layer during fetal growth. And in a smaller number of cases, the tendency to form cysts runs in families.
The Main Types of Skin Cysts
People sometimes call every lump under the skin a “sebaceous cyst,” but that label is misleading. True sebaceous cysts arising from sebaceous glands are actually uncommon. Most of what people call sebaceous cysts are epidermoid cysts, and the distinction matters because different cyst types behave differently and sometimes require different approaches.
Epidermoid Cysts
These are the most frequently encountered skin cysts. They form when surface skin cells (epidermis) get trapped beneath the skin and continue producing keratin, the protein that makes up hair and the outer layer of skin. The cyst fills with a thick, yellowish, cheese-like material. Epidermoid cysts are slow-growing and painless, and they often have a visible central dot called a punctum, which is essentially the plugged opening of a hair follicle.1PubMed Central. Overview of epidermoid cyst They show up most often on the face, neck, chest, and back. If you squeeze one (which you should not do), the material that comes out tends to have a strong, unpleasant smell because of the breakdown of keratin.
Pilar (Trichilemmal) Cysts
Pilar cysts look and feel similar to epidermoid cysts, but they originate from a different part of the hair follicle and have a distinct wall structure under the microscope. About 90 percent of pilar cysts appear on the scalp, and they tend to run in families. A study of 60 families found that pilar cysts followed an autosomal dominant pattern of inheritance in the majority of cases, meaning that if one parent carries the gene, each child has roughly a 50-50 chance of developing them.2Clinical and Experimental Dermatology. Hereditary trichilemmal cysts They are more common in women and sometimes appear in clusters.
Dermoid Cysts
Dermoid cysts are present from birth, even if they are not noticed until later in life. They form during embryonic development when skin cells become trapped along fusion lines of the body. What sets them apart is that their walls contain structures you would normally find in skin: hair follicles, sweat glands, and sometimes even bits of cartilage or bone. If the wall of a cyst lacks these extra structures, it is classified as an epidermoid or keratin cyst instead.3PubMed Central. Characteristics of Dermoid Cyst of the Auricle Dermoid cysts are most often found near the eyebrows, along the nose, or behind the ears.
Hidrocystomas and Steatocystoma Multiplex
Hidrocystomas are small, fluid-filled cysts that arise from sweat glands. They typically appear around the eyes as translucent bluish bumps and can fluctuate in size with temperature and humidity, since sweat glands respond to environmental conditions. Classification of these cysts has been debated among dermatologists, because some tumors originally labeled as one subtype turn out to be a different one under closer examination.4PubMed. Apocrine cystadenoma, apocrine hidrocystoma, and eccrine hidrocystoma: three distinct tumors defined by expression of keratins and human milk fat globulin 1
Steatocystoma multiplex is a rarer condition in which dozens or even hundreds of small oil-filled cysts develop across the chest, arms, and torso. The appearance can have a significant impact on quality of life, particularly in younger patients.5Dermatologic Surgery. Carbon Dioxide Laser Perforation and Extirpation of Steatocystoma Multiplex Each cyst is small, but the sheer number of them makes treatment challenging.
What Causes Cysts to Develop
Most skin cysts are not caused by any single dramatic event. A plugged hair follicle, a minor cut, or chronic friction against clothing can be enough to push surface cells into deeper tissue. Acne is a particularly common precursor, because inflamed follicles are already disrupted and prone to trapping cells below the surface. Acquired cysts are most often of traumatic origin, resulting from an implantation or downward displacement of an epidermal fragment into the dermis.3PubMed Central. Characteristics of Dermoid Cyst of the Auricle
Genetics play a clear role in certain types. Pilar cysts, as noted above, run in families with a strong inheritance pattern. Some people are simply more prone to developing cysts, and it is not unusual for them to develop new ones throughout adulthood. Hormonal shifts may also contribute, which helps explain why certain cyst types are more common during the years of peak hormonal activity.
Less commonly, multiple epidermoid cysts appearing together can be associated with inherited syndromes. Gardner syndrome, for example, involves a mutation in a specific gene and can cause epidermoid cysts alongside other growths. This is rare enough that a person with one or two routine cysts should not worry about it, but a doctor might investigate further if someone develops many cysts at an unusually young age.
How Doctors Diagnose a Skin Cyst
Most skin cysts can be diagnosed by a doctor simply by looking at them and feeling them. A slow-growing, firm, movable lump under the skin with a visible punctum is a strong indicator of an epidermoid cyst. No testing is needed in straightforward cases.
When the diagnosis is less clear, or when the cyst is in an unusual location or behaving unexpectedly, imaging can help. On ultrasound, an epidermoid cyst appears as a well-defined, round-to-oval mass sitting in the fatty tissue just beneath the skin. It does not have its own blood supply, which helps distinguish it from tumors that do. MRI can also be useful in distinguishing cysts from other growths; epidermoid cysts show specific signal patterns that radiologists can recognize.1PubMed Central. Overview of epidermoid cyst These imaging features become particularly valuable when a cyst is deep, large, or in a location where surgery would be complex.
If there is any doubt about whether a lump is a cyst or something else, a biopsy settles the question. The removed tissue is examined under a microscope to confirm that the lining is made of skin cells producing keratin, rather than abnormal or cancerous cells.
When Cysts Cause Problems
An uncomplicated skin cyst sits quietly under the skin and causes no symptoms beyond the cosmetic concern of a visible bump. Problems start when a cyst becomes inflamed or infected.
Inflammation can happen without any bacteria being involved. If the cyst wall ruptures internally, keratin spills into the surrounding tissue, and the immune system treats it as a foreign invader. This triggers redness, swelling, warmth, and pain that can mimic an infection. The release of these materials can stimulate inflammatory pathways that amplify the reaction.6PubMed. Impaired Notch-MKP-1 signalling in hidradenitis suppurativa: an approach to pathogenesis by evidence from translational biology This is why a cyst can become red and tender even when no bacteria are present.
True infection, on the other hand, involves bacteria colonizing the cyst contents. The most common culprit by far is Staphylococcus aureus, which dominated the bacterial isolates recovered from infected epidermoid cysts in a microbiology study. Group A streptococcus and E. coli were also found, but far less frequently.7JAMA Dermatology. Microbiology of Infected Epidermal Cysts An infected cyst can develop into an abscess that requires drainage and sometimes antibiotics.
This is one reason why squeezing or popping a cyst at home is a bad idea. You can rupture the wall inward, triggering inflammation, or introduce bacteria through the skin surface, leading to infection. The cyst also almost always comes back after being squeezed, because the sac wall remains intact beneath the skin and simply refills.
Can a Skin Cyst Become Cancerous
This is one of the most common concerns people have about skin cysts, and the short answer is that malignant transformation is exceedingly rare. The reported incidence of squamous cell carcinoma arising within an epidermoid cyst ranges from roughly 0.01 to 0.05 percent. Since the first documented cases, fewer than 50 well-characterized instances have been reported in the medical literature, most commonly on the head, neck, trunk, and perineum.8Cureus. Malignant Transformation of a Sebaceous Cyst Into Squamous Cell Carcinoma in an Elderly Male Patient
Risk factors that have been linked to this rare transformation include chronic inflammation, repeated infections, ongoing mechanical irritation, ultraviolet exposure, and possibly HPV infection.8Cureus. Malignant Transformation of a Sebaceous Cyst Into Squamous Cell Carcinoma in an Elderly Male Patient A cyst that has been inflamed and re-inflamed over many years has a marginally higher risk than one that has been left alone. That said, the overall probability remains tiny. A cyst that is rapidly growing, firmly fixed to deeper tissue, or ulcerating through the skin deserves a prompt medical evaluation, but the vast majority of stable, slow-growing cysts pose no cancer risk at all.
Surgical Removal
The definitive treatment for a skin cyst is complete removal of the cyst sac. If even a small fragment of the wall is left behind, the cyst can regrow. This is why treatments that simply drain the contents, like needle aspiration, tend to be temporary fixes.
Traditional surgical excision involves numbing the area with local anesthetic, making an incision over the cyst, and carefully dissecting the entire sac away from the surrounding tissue. The wound is then closed with stitches. This approach has a very low recurrence rate but leaves a scar roughly proportional to the size of the cyst.
A less invasive alternative is the minimal excision technique, which involves making a much smaller incision of only about two to three millimeters. The cyst contents are squeezed out through this small opening, and then the collapsed sac wall is pulled out through the same hole. Because the incision is so small, stitches are often not needed.9American Family Physician. Minimal excision technique for epidermoid (sebaceous) cysts The tradeoff is that it can be harder to ensure every bit of the wall has been removed, which makes recurrence slightly more likely than with a full excision.
Timing matters. Surgeons generally prefer to remove cysts when they are not actively inflamed. An inflamed or infected cyst has swollen, fragile tissue around it, making complete removal more difficult and increasing the risk of complications. If a cyst is infected, a doctor may first drain the abscess, prescribe antibiotics if needed, and schedule the definitive excision for several weeks later once the inflammation has settled.
CO2 Laser and Newer Techniques
For people who are concerned about scarring, particularly when a cyst is on the face, CO2 laser-assisted removal has become an appealing option. The technique uses a carbon dioxide laser to create a small opening in the skin, through which the cyst contents and wall are extracted.
A study comparing CO2 laser excision to conventional surgery for facial epidermoid cysts found a dramatic difference in scar size. The average scar after laser excision measured about 0.3 cm at twelve months, compared to about 1.2 cm after conventional surgery. Recurrence rates were slightly higher with the laser approach (roughly 8 percent versus 3 percent for traditional surgery), but the difference was not statistically significant.10PubMed Central. Comparison of complete surgical excision and minimally invasive excision using CO2 laser for removal of epidermal cysts on the face For cysts smaller than about two centimeters, laser excision is a reasonable choice when cosmetic outcome is the priority.
Another study treated 25 patients with small, non-inflamed epidermoid cysts using the CO2 laser method and reported that all patients were satisfied with the cosmetic results, with minimal scarring and low recurrence.11PubMed Central. Minimally Invasive Excision of Epidermal Cysts through a Small Hole Made by a CO2 Laser For cysts that are already infected, combining a CO2 laser incision with photodynamic therapy has shown promise. The photodynamic component uses a light-activated agent to kill bacteria without relying on antibiotics, which avoids the issue of antibiotic resistance. This combination was found to promote faster wound healing and reduce scar formation.12PubMed. Efficacy of the combination of minimally invasive CO(2) laser incision with photodynamic therapy for infected epidermoid cysts
What About Cysts That Do Not Need Surgery
Not every skin cyst requires removal. If a cyst is small, painless, and in a location where it does not bother you, leaving it alone is a perfectly valid option. It is not “ticking time bomb” territory. Many cysts remain stable for decades.
Reasons to consider removal include cosmetic concerns, location in an area prone to irritation (a waistband line, for instance), recurrent inflammation or infection, rapid growth, or uncertainty about the diagnosis. A cyst on the scalp that catches on a comb, or one on the neck that rubs against a collar, may justify removal even if it is not medically urgent.
For certain cyst types, injection-based treatments can be considered. Corticosteroid injections into inflamed cysts can shrink the inflammation temporarily, though they do not eliminate the cyst itself. In digital mucous cysts, which form near finger joints and are a distinct category, intralesional injections of corticosteroids achieved complete resolution in about 40 percent of cases, though multiple treatment sessions were sometimes required.13PubMed Central. Efficacy of Bleomycin Intralesional Injection for Treating Digital Mucous Cysts: A Comparative Study of Corticosteroid Intralesional Injection and Surgical Excision These injections are specific to certain cyst types and are not a substitute for excision when definitive treatment is desired.
Common Misconceptions
The confusion between “sebaceous cysts” and epidermoid cysts leads to a surprising amount of misinformation. One persistent myth is that cysts form because of poor hygiene. While keeping skin clean is generally good practice, cysts are not caused by dirt or inadequate washing. They result from structural changes beneath the skin surface that no amount of scrubbing can prevent.
Another misconception is that warm compresses will make a cyst go away. Warm compresses can help bring an infected or inflamed cyst closer to the surface and may ease discomfort, but they cannot dissolve the cyst wall. The sac has to be physically removed for the cyst to truly resolve. Similarly, “drawing salves” and various home remedies marketed online for cyst treatment may help with superficial inflammation but do not address the underlying structure.
People also commonly confuse cysts with lipomas, which are benign lumps made of fat cells rather than trapped skin cells. Lipomas tend to be softer and more pliable than cysts, lack a punctum, and sit slightly deeper in the tissue. Both are harmless in the overwhelming majority of cases, but they are different things with different causes.
Cysts That Keep Coming Back
Recurrence is one of the most frustrating aspects of dealing with skin cysts. If a cyst was drained or incompletely excised, the remaining wall fragments can regenerate a full cyst over months to years. Some people also seem biologically prone to forming new cysts in different locations, even after successful removal of previous ones.
If you have had a cyst recur after excision, it is worth discussing with your surgeon whether the entire wall was removed. For people with pilar cysts on the scalp, recurrence in the same spot may mean that the excision was incomplete, while new cysts appearing at different sites reflect the underlying genetic tendency. In the case of steatocystoma multiplex, where cysts appear in large numbers, the goal of treatment is often management and cosmetic improvement rather than complete cure, since new cysts may continue to form over time.
For recurrent epidermoid cysts in cosmetically sensitive areas, CO2 laser techniques offer a reasonable balance between thorough removal and minimal scarring. The slightly higher recurrence rate compared to traditional surgery is often an acceptable tradeoff when the alternative is a conspicuous scar on the face or neck. Having a frank conversation with a dermatologist about your priorities, whether that is lowest recurrence risk or best cosmetic outcome, helps guide the choice of technique.