Epidermoid cysts are small, lumps that develop under the skin. These common cysts are sometimes mistakenly called sebaceous cysts. However, this isn’t the correct term for these types of growths. They don’t cause other symptoms and are never cancerous.

Epidermoid cysts are often found on the head, neck, back, or genitals. They range in size from very small (millimeters) to inches across. They look like a small bump, and the overlying skin can be skin-colored, whitish, or yellowish in color.

They’re filled with cheesy-like, white keratin debris. They’re typically painless. Although, they can become inflamed and irritated. They don’t require removal unless bothersome or the diagnosis is in question.

Buildup of trapped keratin usually causes epidermoid cysts. Keratin is a protein that occurs naturally in skin cells. Cysts develop when the protein is trapped below the skin because of disruption to the skin or to a hair follicle.

These cysts may develop for a number of reasons, but trauma to the skin is typically thought to be the main cause. When numerous, an underlying genetic disorder such as Gardner syndrome may be the cause.

To diagnose epidermoid cysts, your healthcare provider will examine the bump and surrounding skin, as well as request your medical history. They’ll ask for details on how long the bump has been present and whether it has changed over time.

Healthcare providers can usually diagnose an epidermoid cyst by examination only, but sometimes an ultrasound or a referral to a dermatologist is needed to confirm the diagnosis.

Epidermoid cysts typically don’t go away completely on their own, although they may shrink to an unnoticeable size and then grow again. Thus, a dermatologist’s surgical intervention is needed to resolve the condition.

Since epidermoid cysts aren’t dangerous, they don’t pose a health risk. Many are never treated.

If the cyst becomes red, swollen, or painful, changes in size or character, or becomes infected, treatment may be desired. In such cases, treatment options typically include antibiotics. Sometimes the cyst may also be drained or injected with a steroid solution.

If you want complete resolution of the cyst, you’ll typically need to have it surgically removed. Usually, this is delayed to a later date if the cyst is currently inflamed.

In almost all cases, epidermoid cysts cause no long-term problems, although they can be associated with genetic diseases that may have medical consequences.

Squeezing out the contents of the cyst on your own can lead to inflammation and/or infection, so it’s best to leave the cyst alone. It can also lead to scarring around the cyst, which can make removal very difficult and result in larger surgical scars.

Once a cyst is drained, it’s very possible that the cyst will grow back. If there’s any significant change in a cyst, it’s recommended that you see your healthcare provider.