What Are Epidermoid Cysts (Sebaceous Cysts)?

Written by Gina Shaw, Kristen Fischer
Medically Reviewed by Zilpah Sheikh, MD on August 13, 2025
7 min read

If you have a bump on your skin that’s not painful, it may be a skin cyst. There are two kinds of skin cysts: epidermoid and sebaceous cysts. Sometimes they’re thought to be the same, but they differ.

An epidermoid cyst, which also is called an epidermal inclusion cyst, feels like a bump underneath your skin. These cysts are filled with the protein keratin.

Sebaceous cysts, on the other hand, are filled with sebum. This substance is made in your sebaceous glands, which are located in your hair follicles, and keep your skin moist.

Epidermoid cysts are the most common type of skin cysts.

Cysts can develop for many reasons — and sometimes for no obvious reason. They are more common in men than in women.

“Cysts typically present as slow-growing, smooth, and mobile lumps under the skin,” explains Danilo C. Del Campo, MD, a dermatologist from Chicago. A cyst can look like other skin issues, which is why seeing a board-certified dermatologist in person is important.

Most of the time, a cyst doesn’t need to be treated, and it will usually be painless. But if it becomes sore or infected, you may need treatment. If you have any concerns, your doctor can confirm if the bump on your skin is an epidermoid cyst.

An epidermoid cyst (sebaceous cyst) can be round or dome-like in shape. There may be a dark dot in the center of the cyst, which will appear pink, red, or darker than your natural skin tone. The cyst can range in size from about 0.25 inches to more than 2 inches. It may feel warm to the touch and seem to move when you push on it.

What are epidermoid cysts filled with?

Epidermoid cysts are filled with keratin — a protein your body makes. If your doctor drains the cyst, the keratin will be thick and yellow, with an unenjoyable odor.

Where do epidermoid cysts form?

You can get epidermoid cysts practically anywhere on your body. They can appear on your:

  • Face
  • Neck
  • Chest
  • Back
  • Scalp
  • Arms
  • Legs
  • Genitals

Epidermal inclusion cysts are created when a hair follicle, which is where hair grows from, is blocked.

Cysts form when your skin cells die but aren’t shed from your body. Instead, the skin cells build up, trapping more skin cells and keratin under the surface of your skin.

Cysts can also develop in areas where you don’t have hair follicles. If you’ve had a trauma to your skin, a cyst can develop in that spot, too. In fact, an injury can push your skin cells below the top layer of your skin, creating a pocket where keratin builds up.

Who is at a risk of developing epidermoid cysts?

Anyone can develop a skin cyst. Epidermoid cysts can show up at any age but most often happen when you’re aged between 20 and 60 years. Rarely, they occur before puberty.

You may be at risk if you have a rare genetic condition, which can cause your body to develop multiple epidermoid cysts. These conditions can include:

  • Favre-Racouchot syndrome
  • Gardner syndrome (familial adenomatous polyposis)
  • Gorlin syndrome (basal cell nevus syndrome)
  • Human papillomavirus

Some medications can increase your risk of developing epidermal inclusion cysts, including:

  • BRAF inhibitors
  • Cyclosporine
  • Imiquimod

Infections can occur if there’s a bacteria in the cyst that makes it painful, discolored, or swollen. If you develop an infection in the cyst, you can treat it with antibiotics.

A normal painless cyst can become bothersome if it becomes swollen or tender, too.

If the cyst breaks, it may swell or become painful. A yellow, odorous discharge will drain from it.

“Most [cysts] are benign but can become inflamed, infected, or uncomfortable,” Del Campo says. In some cases, what appears to be a cyst may actually be a different type of growth that requires further testing or treatment, he adds.

Is an epidermoid cyst painful?

They generally aren’t painful but can be if they become infected.

Your health care provider will look at the bump and ask about your symptoms. They can also conduct tests to ensure that the bump is a harmless skin cyst. Tests may include an ultrasound or a CT can. Both imaging tests are painless.

Your doctor may wish to take a biopsy of the skin cyst, which is when the doctor removes some skin cells from the cyst so they can confirm if the cells are harmless. You may have some mild pain during and after the procedure. Your doctor may shave off cells from the bump or cut more deeply into it. Sometimes, doctors remove the entire bump.

Is it an epidermoid cyst or a tumor?

It’s important to know if you’re dealing with a bump that’s not harmful or potentially cancerous. Most of the time, epidermal inclusion cysts aren’t harmful, but cases can occur when cancer forms in the cyst. These types of cancer may include squamous cell carcinoma and basal cell carcinoma — two kinds of skin cancer.

A few red flags that should warrant a visit to the doctor include:

  • Signs of infection such as pain, skin discoloration, swelling, and/or oozing
  • The bump is growing quickly
  • The diameter of the bump is above 5 centimeters

If none of those occur, keep an eye on your cyst and monitor it for any changes.

Some cysts may shrink temporarily, but most do not go away completely without treatment, Del Campo says.

These are some other options to take care of your cyst.

  • A warm, moist cloth on the area might help it drain and heal, but it’ll probably come back. (If it drains, the stuff that comes out will probably smell bad.)

Your doctor may use these options to treat a cyst.

  • Draining the cyst. The doctor cuts the cyst and pushes out the gunk inside. Cysts can still return after this.
  • Injecting medicine into the cyst to reduce swelling if it’s tender, swollen, or growing.
  • Removing it by a minor surgery to take out the entire cyst wall. This usually keeps them from coming back.
  • Laser removal.

How to remove epidermoid cysts

If your doctor advises that you remove the cyst, the procedure will involve:

  • Making an incision: The doctor will open the cyst and relieve the fluid inside of it. This doesn’t remove the entire capsule around the cyst, though it may ease swelling and inflammation.
  • Cyst removal: Your doctor will give you a local anesthetic, which will keep you from feeling pain but keep you awake. They’ll cut out the outer part of the cyst that was holding the keratin.

If you try to skip the doctor, it could backfire on you. If you try to pop and drain the skin cyst yourself, it could lead to an infection. The cyst will also likely come back again.

After removing an epidermoid cyst, you may have some bleeding or scarring. The removal may cause an infection, which your doctor will monitor.

A few dos and don’ts to help if you have an epidermoid cyst.

  • Don’t try to pop or drain the cyst yourself. “Trying to squeeze or pop a cyst at home is a common mistake,” Del Campo adds. “This often worsens inflammation, increases the risk for infection, and can lead to scarring,” he says.
  • Don’t avoid a doctor. “Cysts should be treated in a medical setting to avoid complications,” Del Campo says.
  • Do keep it clean by washing with warm soap and water.
  • Do apply a bathwater-warm washcloth on it for 20-30 minutes, three to four times a day, to help soothe it and speed healing.
  • Do cover the cyst with a bandage if it starts to drain and make an appointment with your doctor.

Epidermoid skin cysts tend to form randomly. You can try to avoid an injury or a trauma to your skin, and treat any skin conditions you may have, to reduce your risk for an epidermoid cyst. Otherwise, there’s no guarantee that you can prevent the cyst.

Epidermoid or epidermal inclusion cysts occur when keratin builds up under your skin. They differ from sebaceous cysts, which fill with sebum from your skin.

Epidermoid cysts are usually not a problem, but they can be if the cyst is in a visible spot or a spot that becomes irritated. Infections can occur in cysts, but they’re treatable with antibiotics. A doctor can remove a cyst, which is generally taken away for good, but not always.

“Although skin cysts can fluctuate in size depending on the amount of inflammation and cyst contents within, they typically do not completely go away on their own and have a potential of growing back,” says Linna Gali, MD, a dermatologist at Henry Ford Health in Michigan.

Whatever you do, don’t try to pop it yourself. That can cause it to rupture. It can also lead to inflammation and infection.

“This also makes the cyst harder to remove in the future because it can cause the cyst to become more scarred or bound down in the skin,” says Gali.

Is an epidermoid cyst dangerous?

Talk to your doctor to confirm that a cyst is not cancerous. Otherwise, the cysts aren’t dangerous, though you should monitor yours if it seems to be getting bigger or irritated.

Can epidermal cysts be cancerous?

In rare cases, cancer can develop in the cyst.

Are epidermoid cysts contagious?

No, these types of skin cysts are not contagious. This means you can’t spread one to other people, or get one if you’re around another person who has one.