Where do sebaceous cysts form?

Sebaceous cysts are round, smooth lumps that occasionally form under the skin. They most often appear on the face, neck, back, upper chest, arms, and groin, where oil is most often produced. Because of their elevated appearance and firm texture, sebaceous cysts may appear similar to more concerning cancerous lumps, but they are not cancerous and can be treated easily.

What is a sebaceous cyst?

Some glands on the skin secrete an orange, oily substance called sebum, which helps maintain skin and hair integrity. When these glands become clogged or covered with skin cells, the sebum continues to accumulate but is unable to drain. As a result, the surrounding skin shell fills up with the oil, and a sebaceous cyst is formed.

Similar cysts called epidermoid cysts can also form on the skin. The difference is that epidermoid cysts contain only dead skin cells, while sebaceous cysts are filled with sebum. Sebaceous cysts also differ from pimples in that the latter are infected hair follicles, while the former are covered sebum glands.

Symptoms of a sebaceous cyst

While sebaceous cysts are not dangerous, some symptoms do present themselves. They include:

  • A smooth, firm, raised area on the skin
  • Redness on or around the lump
  • Oozing of a yellowish-orange, semi-solid substance
  • Pain around the raised area

These symptoms are generally not dangerous but can be uncomfortable. Sometimes, sebaceous cysts can get infected. If this happens, they will need to be treated. 

After being left untended for some time, the sebum inside a sebaceous cyst may harden into a cheese-like semi-solid that can ooze out of the skin shell to relieve pressure. This waxy substance tends to be either orange, yellow, or white and may give off an unpleasant smell similar to foot odor. 

Causes of a sebaceous cyst

The direct cause of a sebaceous cyst is the obstruction of sebaceous glands by sebum or skin cells, but this can be the result of multiple factors. The most common underlying causes of sebaceous cyst formation are:

  • A ruptured hair follicle caused by previous acne
  • An incorrectly formed sebaceous gland
  • Prior damage to the surrounding area

It is also possible that sebaceous cysts will form without any apparent underlying cause.

Who can get a sebaceous cyst?

Sebaceous cysts are common among all people, but they do appear more frequently in men than in women. They often appear on areas of the body with the most hair and oil glands, as these regions have the most sebaceous glands.

Diagnosis/tests for sebaceous cysts

A simple physical exam by your doctor is generally all that’s required to diagnose a sebaceous cyst. However, your doctor may take a skin culture or a tissue sample (biopsy) if the cyst seems to be infected.

Treatments for sebaceous cysts

Infection is the most urgent reason for treating a sebaceous cyst, but pain, redness, or cosmetic concerns may also constitute a need for treatment. Rupturing is the most common cause of infection.

Sebaceous cysts sometimes go away by themselves, but they may remain indefinitely. If one remains for more than two weeks and you feel it needs to be treated, talk to your doctor. Sometimes a sebaceous cyst may reappear in the same location after it has been treated. 

If your sebaceous cyst needs treatment, your doctor may inject with steroids to reduce inflammation around the area. If it is infected, they may give you an antibiotic, too. If the swelling and redness persist, your doctor may need to lance the cyst. This is done by puncturing holes into the cyst to remove any built-up fluid or skin cells inside and reduce inflammation. 

If the sebaceous cyst returns after being lanced, it may need to be surgically removed. To do this, the doctor will cut out the cyst after applying a minor anesthetic. The procedure is generally considered very mild and is done on an outpatient basis. If the cyst is red or inflamed before the procedure, that may be a sign of infection, and your doctor may postpone the surgery until the swelling goes away.

Side effects of treatment for sebaceous cysts

There are no known side effects of treating a sebaceous cyst. Although they may appear concerning at first sight, sebaceous cysts present minimal danger. They can be painful and a nuisance, but they can easily be treated. 

Most often, your doctor will treat your cyst with steroids or antibiotics if it becomes infected. Sometimes, minor surgery may be required — though your cyst may return in the future.

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Medically Reviewed on 3/16/2021
References
SOURCES:

Cedars-Sinai: "Epidermoid Cysts of the Skin."

Harvard Health: "Sebaceous Cysts."

Johns Hopkins Medicine: "Sebaceous Cysts."

Mayo Clinic: "Epidermoid cysts."

Northwestern Medicine: "Causes and Diagnoses of Sebaceous Cysts."