What Is a Sebaceous Cyst?

A sebaceous cyst—also known as a steatocystoma—is a fluid-filled bump under your skin that develops when the sebaceous (oil) glands in your hair follicles become blocked. These cysts are typically made up of a collection of sebum—an oily substance made up of complex oils such as fatty acids, cholesterol, and squalene, among others.

Sebaceous cysts are often confused with epidermoid cysts—but, they are actually different. Epidermoid cysts are made up of dead skin cells, while sebaceous cysts are oil-filled lumps. Several factors can cause a sebaceous cyst to form, such as hormonal changes during puberty or skin infection and injury. These cysts can cause symptoms like pain, swelling, and redness. But keep in mind: these bumps are usually harmless and can go away on their own or with quick treatment.

Symptoms

Sebaceous cysts are slow-growing cysts that appear as a small lump beneath the skin. They are often painless and do not produce distinctive symptoms unless they become infected. A few common signs and common features of sebaceous cysts include:

• Size: The cyst is a few millimeters to a couple centimeters large
• Color: The cyst appears under your skin and matches your skin tone, but can turn slightly yellow over time
• Shape: The cyst is firm, round, or dome-shaped and filled with an oily substance
• Touch: The cyst freely moves under your skin and may appear tender when you touch it

Sebaceous cysts can appear anywhere on your body but commonly occur in regions rich in sebaceous (oil) glands, such as your neck, scalp, groin, chest, face, and armpits. It's also possible to develop one singular cyst or multiple cysts in the same location.

Causes and Risk Factors

You may develop a sebaceous cyst when the oil glands around your hair follicles become blocked. Sebaceous glands produce and release an oily substance known as sebum. Sebum plays several key functions in your body, such as lubricating your skin, transporting antioxidants to the skin, keeping hair shafts soft, and helping fight bacteria. When your hair follicles become blocked, you can develop a collection of sebum in the follicle which can cause a sebaceous cyst to form.

The following factors can increase your risk of a sebaceous cyst:

• Changes in hormone levels when you're going through puberty
• Trauma, injury, or skin infection
• Being of older age
• Your genetics

Diagnosis

Noticing a bump or lump under your skin can feel scary or concerning. If you develop a bump and aren't sure what may be causing your symptoms, it's a good idea to see your healthcare provider just in case. While sebaceous cysts are usually harmless, these bumps can also mimic the appearance of swollen lymph nodes or lipomas.

At your appointment, your healthcare provider can diagnose a sebaceous cyst through a simple physical exam. They might also ask questions about your medical and family history for proper diagnosis. To confirm a diagnosis and rule out other conditions, your provider may also choose to order some diagnostic tests. These include:

• Ultrasonography: Uses an ultrasound to create detailed images of the cyst
• Bacterial culture: Collects a small sample of your tissue or fluid from the cyst to identify any signs of an infection

Treatment

In most cases, a sebaceous cyst can go away on its own and may not require treatment. If you do need treatment, it's likely because your cyst has become inflamed or infected, or symptoms are interfering with your quality of life. Your healthcare provider can recommend the following treatment approaches:

• Antibiotics: Taking antibiotic medication can help reduce the presence of inflamed cysts and remove any bacterial infection that may be causing your symptoms. These medications can also help shrink the size of your cyst.
• Surgical procedures: In some cases, your provider may recommend removing the cyst entirely with surgery. The exact surgery you need will depend on the size and location of your cyst. A common surgical technique is incision and drainage, which occurs when a provider cuts into the cyst and drains or removes it to reduce symptoms and treat the infection.
• Laser therapy: Carbon dioxide laser therapy can be effective in making small holes in the cyst wall and helping minimize the size of your cyst.

How To Prevent a Sebaceous Cyst

It's not always possible to prevent a sebaceous cyst from forming. But, experts recommend doing your best to avoid trauma, injury, or infection to the skin to lower your risk of developing sebaceous cysts.

Complications

While these types of cysts are usually harmless, a sebaceous cyst may cause complications if it becomes inflamed or infected. Inflammation and infection may cause the cyst to suddenly rupture and cause pain, swelling, and redness of the skin around your cyst.

There is also some risk of experiencing complications if you have surgery to remove your cyst. These risks include scarring of your skin, formation of blisters, and changes in skin tone or hyperpigmentation in the area where the surgery took place. It's also possible that your cyst recurs even after it's been removed.

A Quick Review

Sebaceous cysts are generally harmless and do not cause symptoms. These types of cysts occur when your hair follicles become blocked, causing sebum or oil to accumulate in them. That's why sebaceous cysts are filled with oil. However, when these cysts become infected or inflamed, they can lead to symptoms such as pain, swelling, and redness. If you develop a sebaceous cyst that is causing symptoms, it's best to see your healthcare provider for testing and treatment.