What Is an Epidermoid Cyst? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Medically Reviewed

It’s easy to panic when you notice a lump on your skin. You may wonder if it’s melanoma or another type of skin cancer.

But sebaceous cysts — slow-growing bumps under the skin that can appear on the ears, scalp, face, torso, back, or groin area — are typically harmless. And while they can be irritating (or unsightly), they are not cancerous. Here’s what you need to know — and do — if you have a sebaceous cyst.

The first thing to know is that the term “sebaceous cyst” is often used to describe what is actually an epidermoid cyst. The terms are used interchangeably, but there’s a difference, notes the Cleveland Clinic.

True sebaceous cysts are caused by the glands that secrete the oily matter (sebum) that helps lubricate your skin and the hair, per the Mayo Clinic.

They are not as common as epidermoid cysts, which occur when skin cells accrue under the skin instead of being shed from its surface. This article will mainly focus on epidermoid cysts.

Signs and Symptoms of an Epidermoid Cyst

These dome-shaped cysts can be pea-sized, or grow to a few inches or larger. They grow very slowly, and they’re not painful. If you touch them, you should be able to move them around. They often have a central small black dot, or punctum, through which sebum accumulates.

Sometimes, however, they can become inflamed, infected, or suddenly rupture, which can increase the risk of infection (more on that later). Occasionally, they occur on a site that is constantly irritated, such as a cyst on your neck that rubs against your collar, or one on your back under a bra strap.

Whatever the cause, if you notice redness, tenderness or warmth, that can indicate that the cyst has become infected. You may also notice that the cyst excretes a cheese-like liquid that has a foul smell.

Unpleasant as that may seem, cysts can disappear on their own without treatment, according to Harvard Health.

But if a cyst is bothering you, or becomes painful, it makes sense to see your doctor.

Common Questions & Answers

What is the cause of sebaceous cysts?
Usually when people use the term sebaceous cyst, they’re actually referring to epidermoid cysts. These occur when skin cells accrue under the skin. Sebaceous cysts, which are less common, are caused by the glands that help lubricate skin and hair.
What is a sebaceous cyst filled with?
Sebaceous cysts are filled with sebum, which is the liquid that helps lubricate skin and hair. Epidermal cysts contain dead skin cells that did not get shed from the skin’s surface.
Can you squeeze out a sebaceous cyst?
Do not pop or squeeze the cyst like a pimple. A ruptured cyst could lead to infection. Instead try applying a warm moist compress, which may help the cyst drain.
Do sebaceous cysts go away on their own?
Some sebaceous cysts go away on their own, but, as with epidermal cysts, which don’t tend to go away on their own, they’ll need to be removed if they become infected.
How do you get rid of a sebaceous cyst?
If a sebaceous or epidermal cyst doesn’t cause problems, you probably don't need any treatment. If a cyst becomes inflamed, it can be injected with a steroid to reduce swelling. Cysts that become infected may need to be surgically removed.

Causes and Risk Factors of an Epidermoid Cyst

The surface of your skin, known as the epidermis, consists of thin layers of cells that are constantly shedding. Sometimes, though, when the cells move deeper into the skin, instead of shedding, they can multiply, leading to cyst formation.

Acne can contribute to their development, as can damaged or swollen hair follicles.

Sometimes, injury to the skin may cause a sebaceous cyst.

And as for that secretion that can emerge from the cyst? It comes from the cells that form the walls of the cysts. Those cells secrete a protein, known as keratin. These cysts are also made of fat, and it’s often that substance, or infection, that makes the smell, according to American Family Physician.


How Is an Epidermoid Cyst Diagnosed?

Usually, your doctor can diagnose a sebaceous cyst by examining your skin, though sometimes he or she may perform a biopsy to make sure it’s not a symptom of another condition. Before your exam, it’s a good idea to note any recent skin injuries, when you first noticed the cyst, if you’ve had any other cysts, and if you have a family history of cysts. Your general practitioner will usually be the one to examine you, and then after that you may be referred to a dermatologist.

Prognosis of Epidermoid Cysts

Most sebaceous cysts can be ignored, since they are not dangerous. Some go away on their own; others grow slowly, but unless they are bothering you, or get infected, you don’t need to do anything about them.

To rule out cancer, your doctor may send a cyst specimen to be examined under a microscope. These will turn out to be basal cell carcinoma — the most common form of skin cancer — or squamous cell carcinoma in less than 1 percent of cases, notes StatPearls.

RELATED: What Is Pilonidal Cyst?

Duration of Epidermoid Cysts

Cysts can remain small for years or they can keep growing larger. Sometimes, as noted above, a sebaceous cyst can disappear on its own, but surgery is usually necessary to remove them.

Treatment and Medication Options for Epidermoid Cysts

If a sebaceous cyst does not cause problems and its appearance doesn’t bother you, you probably don't need any treatment, as mentioned above.

Medication and Surgical Options

If a cyst becomes inflamed, a doctor can inject it with a steroid to reduce swelling. Cysts that become infected, on the other hand, may need to be surgically removed. Dermatologists and plastic surgeons can perform this procedure. To do this, your doctor will make a small puncture and remove the contents. But cysts frequently return after removal and will ultimately need to be surgically removed again. If a cyst becomes swollen or infected, antibiotics may be called for before surgery. Larger cysts may also need to be removed if they cause hair loss on the scalp, interfere with clothing (for instance, if a piece of clothing routinely rubs the cyst, causes irritation), or if the cyst is in an obvious place, like the face.

In some cases, your doctor may use a laser to remove the cyst. A study published in April 2019 in Archives of Craniofacial Surgery found that this approach works well with smaller cysts, leaves smaller scars, and may be a suitable replacement for surgery in an area of cosmetic concern, such as the face.

After the treatment, be sure to follow your doctor’s instructions for keeping the wound clean once you get home, and ask if you should return for a follow up visit.

Alternative and Complementary Therapies

If a sebaceous cyst becomes swollen or tender, home treatments may also help. One easy thing to try: applying a warm moist compress, which can help the cyst drain. What not to do: Resist the urge to pop or squeeze the cyst, like a pimple. It won’t end well.

Prevention of Epidermoid Cysts

Unfortunately, there’s no known way to prevent them from developing.

Complications of Epidermoid Cysts

Epidermoid cysts can become infected, as already noted. The telltale signs of infection are redness, inflammation, and skin that feels warm to the touch.

If the cyst ruptures, it can also lead to infection, so it’s important to get treatment right away.

In most cases, however, cysts don’t cause problems, and it’s rare for complications or side effects to occur after treatment or surgery.

RELATED: What Is a Skin Lump?

Research and Statistics: Who Has Epidermoid Cysts?

According to StatPearls, sebaceous cysts are the most common type of skin cyst.

They are most likely to occur when a person is in their thirties or forties. One surprising stat: Men are twice as likely to get them as women.

Black and Hispanic Populations and Cysts

Sebaceous cysts are among the most common dermatologic diagnoses in white, Black, and Hispanic individuals, according to a review, published in the Journal of Drugs in Dermatology, of 16 years of data collected from patient visits to U.S. physicians.


Related Conditions and Causes of Epidermoid Cysts

As mentioned above, these cysts are, very rarely, a sign of cancer. Research also suggests that they can be caused by human papilloma virus (HPV). Those cysts can appear anywhere on the body, but they tend to show up on the palms and feet, according to research published in October 2017 in the Journal of Dermatology.


Resources We Love

The Cleveland Clinic offers has a quick and clear guide to how these cysts develop and how they’re treated.

While these cysts aren’t skin cancer, if you want to know more about what is and isn’t skin cancer, the National Cancer Institute has a wealth of information, including a tool that can help you recognize the signs. But remember: A doctor is the only one who can tell you for sure.

Additional reporting by Paula Derrow and Kathleen Doheny.

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