Causes and Risk Factors of Cysts

Hormones or fluid build up may be to blame but often cysts have no clear cause.

Table of Contents
View All
Table of Contents

A cyst is a closed pocket of tissue that forms somewhere on the body. Unlike tumors, which are caused by abnormal growth of body tissue, cysts are usually filled with air, pus or fluid. Cysts are usually harmless, but they can cause pain, discomfort or complications depending on how large they are or where they appear. There are hundreds of different types of cysts and oftentimes they’re unexplained. But they can also be caused by fluid buildup, hormonal fluctuations or injury. 

This article will cover what causes cysts, including skin cysts, ovarian cysts, and internal cysts. We’ll also cover the factors that might put you at increased risk for developing cysts.

Woman talking to doctor

sturti / Getty Images

Common Causes

There are hundreds of different types of cysts, but it’s most common first cysts to form on the skin, breasts, ovaries or kidneys. The causes of cysts include:

Fluid buildup

The body has many glands that secrete fluids. When these glands become blocked, the fluid can build up, forming a cyst. For example, sebaceous cysts are skin cysts that form just below the surface of the skin, when oil glands become blocked. Bartholin's gland cysts form when the ducts that lubricate the vaginal become blocked. 

Hormonal fluctuations

Hormones play an important role in the development of cysts, particularly for biological females. For example, breast cysts are caused by an imbalance of the hormones estrogen and progesterone. Hormonal imbalances also contribute to ovarian cysts and polycystic ovarian syndrome.


Having an injury can cause a cyst, particularly on your skin. Damaged cells or popped blood vessels can develop into cysts. You can even develop a cyst after getting a piercing, like an ear or nose piercing. 

Uncommon Causes

Rarely, cysts can be caused by a parasite. Hydatid disease and echinococcosis are tapeworm infections that cause cysts throughout the central nervous system, lungs and liver. Trichinellosis is a disease caused by roundworms that causes cysts on the brain.  

Risk Factors

Anyone can get cysts, and they are extremely common. In many cases, doctors don’t know why cysts form. However, there are some risk factors that may increase your risk for cysts. These include:

  • Being female. Many types of cysts are associated with female hormones, including estrogen and progesterone. Some of the most common types of cysts, including breast and ovarian cysts, are found in cisgender women. However, some types of cysts, including renal (kidney) cysts are more common in men. 
  • Age: The risk for some type of cysts increases with age. For example, renal cysts are more common in people who are over 40. Other types of cysts are most common in a certain age bracket. For example, breast cysts are most common in people ages 30-50.


In most cases, doctors don’t know why cysts form. Since there are hundreds of different types of cysts, it’s impossible to make blanket statements about causes and risk factors. However, there are some causes that are particularly common, including hormonal fluctuations, fluid back-up and injury. If you have cysts that are uncomfortable or bothering you for any other reason, talk to your doctor. 

A Word From Verywell

In most cases, cysts are nothing to worry about. They’re very common, and almost everyone will have one at some point or another. However, if you have any questions or concerns about how often you experience cysts or what might be causing them, reach out to your health care provider.

Frequently Asked Questions

  • What causes a cyst?

    There are many different causes for cysts, and many times doctors don’t know why they occur. However, hormonal fluctuations, fluid backup and injury are common causes. 

  • Are cysts cancerous?

    It’s very rare for a cyst to be cancerous. However, there’s some research that says breast cysts might increase the risk of breast cancer for some people. Talk to your doctor about your specific risk factors.

  • What’s inside a cyst?

    Usually, cysts are filled with fluid, pus or air. Occasionally, they can contain other types of tissue like bone or hair. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Cancer Institute. Cyst.

  2. Harvard Health Publishing. Cysts (overview). March 9, 2022.

  3. Stachs A, Stubert J, Reimer T, Hartmann S. Benign breast disease in women. Dtsch Arztebl Int. 2019;116(33-34):565-574. doi: 10.3238/arztebl.2019.0565

  4. U.S. Department of Health and Human Services. Office on Women’s Health. Polycystic ovary syndrome. April 1, 2019.

  5. Better Health Channel. Cysts.

  6. Office on Women's Health. Ovarian cysts.

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.