Skin Cysts (Sebaceous Cyst)

A skin cyst (Sebaceous cyst) is a fluid-filled protrusion originating from the skin layers, and lying just under the surface of the skin. It is usually harmless, and may be caused by many common conditions, so it does not always require treatment.

Sebaceous cysts or trichilemmal cyst. Schematic illustration of a segment of skin with Sebaceous cyst - Image Credit: Designua / Shutterstock
Sebaceous cysts or trichilemmal cyst. Schematic illustration of a segment of skin with Sebaceous cyst - Image Credit: Designua / Shutterstock

Gross Appearance

A skin cyst is usually rounded and dome-shaped, with a yellowish or whitish appearance. In many cases it has a dark-coloured spot on the top which breaks down spontaneously or on squeezing, to discharge some pus.

Sebaceous Cyst on Woman
Sebaceous Cyst on Woman's Back - Image Credit: jarabee123 / Shutterstock

The size may vary, some cysts being tiny and others as big as a few centimeters across. Most cysts grow slowly, and are not painful. However, they may become infected, in which case they turn red and start to hurt. The skin around them becomes swollen, and they may start to ooze foul-smelling pus.

Skin Cyst Location

Skin cysts may occur in various sites over the body, depending on the type. The most common type, called epidermoid cysts, may be found over the face and neck, the chest and shoulders, and the genital skin.

Skin cysts may occur in individuals with acne more commonly than in others. Young and middle-aged people are more likely to develop skin cysts, and prepubertal children rarely have skin cysts. Skin which has been previously damaged, or is affected by acne, is more likely to develop skin cysts.

Pilar cysts form around the pilosebaceous units, and often occur on the scalp. They do run in families, unlike most skin cysts. Middle-aged women are most often affected, but men are also not spared.

A chalazion, or Meibomian cyst, is a cyst that forms on the inner aspect of the eyelid, and is granulomatous rather than containing simple clear fluid.

Mechanism of Formation

The normal process of skin maturation involves the upward migration of keratinized cells through the skin layers, to reach the top as dead cells which are eventually shed. When this process is disrupted for any reason, the intensely keratinizing cells move deep into the middle of the skin layers, and proliferate to form a sac. The keratin they secrete accumulates in the center of the cavity, as a dense yellowish paste. If the cyst breaks or is squeezed it will ooze keratin.


Skin cysts are usually benign and resolve on their own, without any specific treatment, especially if they are small and asymptomatic. If they seem to be becoming larger or inflamed, warm fomentation may be helpful to speed up healing.

It is usually inadvisable to break the cyst open, prick it, or squeeze it, to encourage it to heal faster - if it is infected, then this increases the likelihood of sepsis. In some cases, antibiotics may be required.

Sometimes the cyst is located in an awkward or cosmetically unacceptable location. In such cases, minor surgery may be indicated to remove the cyst with a narrow margin of surrounding tissue under local anesthesia. Long-term recurrence may occur in some cases, especially in the scalp or scrotum. Scarring is also inevitable, though the incision is small and will be carefully closed.


Further Reading

Last Updated: Feb 27, 2019

Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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  1. Ke'Avion Jackson Ke'Avion Jackson United States says:

    I have a bump on the back of my arm that has white puss that comes out every time I squeeze it. It Doesn't hurt at all but, it does have a nasty smell to it. It showed up around almost a year ago, and it's been here ever since.

  2. Karen Jones Karen Jones United Kingdom says:

    I am prone to cysts...a lot of different ones according to the gallery i attended but I have one on the lower part of my spine that gets infected and secretes that green goop an then produces the hard keratin stuff...what type of cyst is that please?

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