Sebaceous cyst

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at June 20, 2016
StartDiseasesSebaceous cyst

Sebaceous cysts (SCs) are harmless growths that occur right under the skin and cause raised bumps. These growths are non-cancerous and contain mainly liquid or semi-solid matter. Sebaceous cysts commonly refer to epidermal cysts (alternately known as epidermoid cysts, keratin cysts, and epidermal inclusion cysts).


Definition & Facts

The sebaceous area of the skin is in the layer known as the dermis, or the layer below the epidermis, an area that is approximately 0.05 to 1.5 millimeters deep. The dermis is 1.5 to 4 millimeters thick, containing:

The sebaceous gland secretes an oily substance known as sebum that coats the hairs and skin. The sebum secretion is created in an attempt to create a waterproof the skin and hairs to prevent the skin from drying out. 

During puberty, the sebaceous glands secrete sebum in excess making the skin oily, sweaty, and odorous; the liquid also creates blemishes and/or acne. When the sebaceous gland becomes over-engorged and blocked, this creates a sebaceous cyst. In extremely rare cases, some sebaceous cysts can become benignly tumorous or cancerous.

Symptoms & Complaints

Since the cysts are underneath the skin’s surface, they irritate the epidermis upon being blocked, irritated or inflamed. The area around the cyst may become warm, tender, sore and/or odorous. The odor that the white to gray pus emits is similar to a pungent cheese odor.

Symptoms of sebaceous cysts are usually evident on the face, neck, and trunk (the trunk consists of the chest, midsection, abdomen and pelvic area). Sebaceous cysts that develop often grow slowly over time and are not painful.

The cysts can become engorged, forming pale, movable lumps underneath the skin. The palms of the hands and the soles of one’s feet are the only areas of the body that cannot develop cystic growths.


The causes of SCs are usually due to another problem that has affected the skin or hair follicle. Sometimes when there is a laceration, scrape or other damage to the skin, the area becomes saturated with white blood cells and platelets. Whenever the wound heals, the skin readies the area with collagen. However, sometimes there is too much collagen that is grown to cover the wounded area, causing the glands around the base of a hair to become clogged.

Skin can also play a role in the creation of SCs. Since humans shed, on average, around 720,000 to 960,000 cells per day, a good chance of those cells becoming lodged in a hair follicle is relatively high. When skin becomes lodged inside a hair follicle, this creates a blockage. This allows cultivation of bacteria to grow which are known as Propionibacterium acnes (also known as P. acnes). Sometimes, when acne damages the hair follicle, the area is more likely to become cystic, causing sebaceous cyst (epidermoid cyst) growths to occur under the skin.

Diagnosis & Tests

Physicians and doctors can usually diagnose a cyst simply by observing it in a physical examination. In other cases, some tests can be done in order to properly diagnose the cyst as a sebaceous cyst. One test performed to check the skin is a skin lesion biopsy. There are four subcategories of lesion biopsies:

A shave biopsy is performed via a razor blade tool that extracts the epidermal skin layers from the skin’s surface. A punch biopsy is performed by a circular razor punch tool that is used to cut a section of the skin in order to test the area for the possibility of being a sebaceous cyst. Excisional and incisional biopsies are extractions of the affected area by means of a surgical knife; however an incisional biopsy only removes part of the affected area.

In other tests, skin cultures may be ordered to check if the cyst contains any bacteria. The skin will then be watched over the course of the next 21 days to see if the culture develops. When the culture becomes sufficiently developed to determine the type of virus, bacteria or other pathogen that is growing, proper treatment will then be put in place.

Treatment & Therapy

There are three different medical methods used to treat SCs. One method to reduce swelling of the area is by cortisone (corticosteroid) injection. Corticosteroids work to reduce inflammation caused by a variety of diseases. To treat sebaceous cysts, cortisone can be injected directly into the site of the cyst.

Another method to treat sebaceous cysts is by oral medication. Antibiotics are commonly administered to patients whose cysts are infected with bacteria. The last means of treating an SC is to remove it through surgery. Though the cyst can be removed and heal, there still is a chance of it returning if it is not entirely eliminated.

There is a home remedy that may ease the draining of the cyst. One can either microwave a small washrag or towel in a bowl of water or pour boiling water into a bowl containing the washrag. He/she can then remove the washrag/towel carefully examining the temperature to ensure that he or she doesn’t burn him or herself upon placing it directly onto the skin.

Prevention & Prophylaxis

The only prevention that is applicable to sebaceous cysts is for those who are suffering from acne. For individuals who have recurring or chronic acne, it is important to control acne with a regimen of medication. Seeking medical advice for the best creams or oral supplements is recommended.