(905) 906-7546
Sebaceous cysts are a common type of non-cancerous skin bump that typically form on areas like the face, neck, scalp, or upper body. They often appear as smooth, round lumps under the skin and are usually painless unless they become irritated or infected. The term “sebaceous cyst” is a bit confusing, because it’s used to describe a couple of different types of cysts. In fact, the vast majority of lumps commonly called sebaceous cysts are actually epidermoid cysts (originating from skin cells), while true sebaceous cysts (arising from oil glands) are relatively rare. Both types look similar and are treated in similar ways, but they have different causes. In this article, we’ll explain what sebaceous cysts are, describe the two main types (epidermoid cysts and true sebaceous cysts), compare their differences, and discuss what causes them. We’ll also take a look at other kinds of skin cysts and outline treatment options. Our goal is to provide clear, reassuring information so you can better understand these common skin bumps.
Epidermoid Cysts (Common “Sebaceous Cysts”)
Epidermoid cysts are the most common type of skin cyst – the ones people frequently (but incorrectly) refer to as “sebaceous cysts”. An epidermoid cyst actually originates from the epidermis (the outer layer of skin) rather than from a sebaceous gland. It forms when surface skin cells (or the lining of a hair follicle) become trapped beneath the skin instead of shedding off as usual. Those cells continue to multiply under the surface and create a sac or capsule. The sac then fills with keratin, a protein that makes up skin, hair, and nails. The trapped keratin inside the cyst becomes a soft, yellowish “cheese-like” material. This is why when an epidermoid cyst drains, it may release a thick, whitish substance (keratin debris) rather than oil.
What causes epidermoid cysts? The primary cause is a blockage or damage in a hair follicle or pore that allows skin cells to collect beneath the skin. Common triggers include skin trauma or irritation. For example, a scratch, a surgical wound, or inflammatory acne can push surface cells deeper into the skin or block a follicle, leading to cyst formation. In some cases, chronic sun damage or other skin conditions that affect the way skin cells shed may also contribute. Rarely, there can be genetic factors, for instance, an inherited condition like Gardner syndrome can predispose a person to multiple epidermoid cysts. Overall, anything that causes skin cells to be “trapped” under the surface (instead of shedding normally) can result in an epidermoid cyst.
How to recognize an epidermoid cyst: These cysts typically appear as small, round bumps just under the skin surface. They are usually skin-colored or have a slight white or yellow tint. Often there is a tiny dark pore (opening) on top of the cyst (called a punctum), which is a remnant of the blocked follicle, though this is not always visible. Epidermoid cysts can range in size from a few millimeters to a few centimeters across and tend to grow slowly over time. They feel firm but movable under the skin. Generally, they are painless and don’t cause issues unless they become inflamed or infected. If an epidermoid cyst becomes
infected, it can become red, swollen, warm, and tender, and might drain pus. It’s important to avoid squeezing these cysts, as doing so can cause the cyst to rupture under the skin and lead to inflammation or infection.
True Sebaceous Cysts (Steatocystomas)
True sebaceous cysts are much less common than epidermoid cysts. The term “sebaceous” refers to sebaceous glands – the oil-producing glands in the skin. A true sebaceous cyst originates from a sebaceous gland (usually one attached to a hair follicle) and is essentially a blocked oil gland. In medical terms, these
are sometimes called steatocystomas when they occur singly (or steatocystoma multiplex when someone has many of them). Unlike epidermoid cysts (which contain keratin), a true sebaceous cyst is filled with sebum – the oily substance that sebaceous glands normally secrete to lubricate the skin and hair.
What causes true sebaceous cysts? They develop when the duct of a sebaceous gland becomes blocked or damaged. Normally, sebum from the gland exits through the hair follicle opening to the skin surface. If that outlet is clogged (for example, by skin trauma, swelling, or debris) or if the gland is injured, the sebum backs up. The trapped oil then accumulates and enlarges the gland into a cyst. In essence, the gland turns into a little oil-filled balloon under the skin. Trauma or injury directly to the sebaceous gland or its duct is a common cause of these cysts. Occasionally, certain genetic conditions can be associated with multiple true sebaceous cysts – for instance, Gardner syndrome (an inherited condition) has been linked to various cysts, including sebaceous ones. However, having a true sebaceous cyst without any genetic syndrome is far more common than the genetic cases.
Comparing Epidermoid vs. Sebaceous Cysts
It’s helpful to summarize the key differences between these two types of cysts. Below is a comparison of
their characteristics and causes:
- Origin: An epidermoid cyst arises from epidermal cells (skin surface cells) or hair follicle cells that get trapped under the skin. A true sebaceous cyst originates from cells of a sebaceous (oil) gland. In other words, epidermoid cysts come from skin, whereas sebaceous cysts come from oil glands.
- Contents: Epidermoid cysts are filled with keratin – a soft, yellow-white, pasty protein material (the same substance found in hair and nails). True sebaceous cysts are filled with sebum – an oily, often yellowish fluid produced by sebaceous glands. Keratin has a thicker, cheese-like consistency, while sebum is more oily. (Neither type typically contains “pus” unless infected.)
- Cause of Blockage: In epidermoid cysts, the blockage is usually in a hair follicle or pore, often due to trauma or acne that causes skin cells to plug the follicle. In true sebaceous cysts, the blockage is in the sebaceous gland’s duct – often due to damage or clogging of the gland outlet. Both result in trapped material (keratin or oil) that builds up inside a sac.
- Frequency: Epidermoid cysts are very common – most of the “sebaceous cysts” people get are of this type. True sebaceous cysts are relatively uncommon by comparison. It’s much more likely that a cyst on your back or face is an epidermoid cyst filled with keratin rather than a true oil-filled sebaceous cyst.
- Location: Both types can occur in similar areas of the body (since hair follicles and sebaceous glands coexist in many places). Epidermoid cysts are often seen on the face, neck, scalp, back, and chest. True sebaceous cysts also appear in oil-rich areas like the face, scalp, and upper body. Pilar cysts (a related type that occurs on the scalp) are sometimes mistaken for sebaceous cysts too, but those are a separate category (more on other cysts below).
- Identifying the Type: Visually and symptom-wise, there is no easy way for a person to distinguish an epidermoid cyst from a true sebaceous cyst – they both look like round subcutaneous bumps and usually feel similar. Even physicians may only suspect which type it is based on location or contents, but definitive identification would require examining the cyst’s contents or its lining under a microscope. Fortunately, since both types are benign and treated in almost the same manner, you typically don’t need to worry about pinpointing the exact type on your own. A healthcare provider will treat the cyst based on its behavior (infected or not, etc.), and if it’s removed, pathology can confirm the type.
Other Types of Skin Cysts
Besides epidermoid and true sebaceous cysts, there are a few other types of skin cysts you might come across. We won’t go into detail on these, but here are a couple of examples:
- Pilar cysts (Trichilemmal cysts): These are cysts that form from hair follicle root sheath cells, most commonly on the scalp. They are usually filled with keratin (like epidermoid cysts) and often run in families. Pilar cysts are firm, dome-shaped bumps on the scalp and can sometimes be multiple.
- Milia: Milia are tiny (1–2 mm) white cysts often seen on the face, especially around the eyes and cheeks. They occur when keratin becomes trapped just under the outer layer of the skin, forming very small, hard white bumps. Milia are common in newborns and can also affect adults. They are completely harmless and often resolve on their own.
Other cyst-like bumps: There are other benign cysts and lump conditions such as dermoid cysts (present from birth, containing skin/developmental tissues), ganglion cysts (fluid-filled bumps near joints like the wrist), and chalazia (cysts in the eyelid caused by blocked oil glands in the eyelid). These differ in location and content from sebaceous or epidermoid cysts, but it’s good to be aware that not every cyst under the skin is of the sebaceous variety. A physician can help identify what type of cyst or lump you have.
Treatment and Removal Options for Sebaceous Cysts
Most sebaceous cysts (whether epidermoid or true sebaceous) are benign and do not necessarily require treatment if they are small and not bothersome. If you have a cyst that isn’t painful, infected, or growing, a common approach is simply to keep an eye on it. Some cysts may remain stable for a long time or even eventually shrink a bit on their own. That said, cysts generally do not go away completely without intervention. If a cyst is causing discomfort, getting frequently irritated (for example, by rubbing on clothing), or if you simply want it removed for cosmetic reasons, a minor removal procedure can be considered.
Important: It is best not to attempt “popping” or squeezing a cyst at home. Squeezing can force the cyst’s contents (keratin or sebum) out through a small opening, but often it can also rupture the cyst capsule inside the skin. This can lead to a painful inflammatory reaction or infection in the surrounding tissue.
In other words, trying to drain it like a pimple can make matters worse and increase the chance of the cyst returning or scarring. If a cyst becomes red, swollen, or tender, it might be infected and you should see a physician for proper care.
Medical treatment options: When you visit a physician for a cyst, they will evaluate its condition. If the cyst is infected (abscessed), the immediate treatment might involve an incision and drainage procedure. In this quick in-office procedure, the area is numbed and a tiny cut is made to drain the pus or keratin out, relieving pressure. You might also receive antibiotics if there is significant infection. It’s important to know that incision and drainage does not remove the cyst capsule, so the cyst may fill up again over time. This is usually a temporary fix when there’s acute inflammation or infection.
For a long-term solution, the cyst (including its wall or sac) needs to be removed completely. The definitive treatment for either type of sebaceous cyst is excision, meaning a minor surgical procedure to cut out the entire cyst. This is often a straightforward outpatient procedure done under local anesthesia (numbing the area). The physician will make a small incision in the skin, carefully dissect out the cyst sac, and remove it entirely. The incision is then closed with a couple of stitches. Removing the whole cyst wall greatly reduces the chance of the cyst coming back. Such cyst removal procedures are typically quick (often 20-30 minutes) and recovery is uncomplicated. You might have a few days of mild soreness and a small scar line that fades with time.
After removal, the cyst can be examined under a microscope (a routine pathology exam) to confirm the diagnosis and ensure there are no unusual cells. However, complications from sebaceous or epidermoid cysts are rare, and they are almost always benign.
Next steps – consultation: If you’re unsure about a lump or cyst on your skin, it’s wise to have it evaluated. You can book a free consultation with a physician who can provide a personalized assessment of your cyst. In a consultation, the doctor will examine the bump and advise you on whether it should be removed
or can be left alone, and they will answer any questions you have. This one-on-one assessment will give you clarity and help you make an informed decision. Remember, sebaceous cysts are common and very treatable. With proper care from a qualified physician, you can have the cyst addressed quickly and with minimal discomfort. Don’t hesitate to reach out for a professional evaluation, it’s the best way to ensure your skin stays healthy and you stay worry-free.