Bartholin glands are two small glands that are located on each side of the vaginal opening. They produce fluid to lubricate the opening to the vagina. If the duct to a Bartholin gland becomes blocked, fluid builds up inside the gland, causing a cyst.
Things like an infection, thick mucus, or swelling can block a Bartholin gland duct and cause a cyst. The cyst can get bigger after sex, because the glands make more fluid during sex.
Infected Bartholin cysts are sometimes caused by sexually transmitted infections (STIs). You can lower your risk of STIs by using a condom when you have sex.
Bartholin cysts that do not cause symptoms do not need to be treated. A Bartholin cyst that is large, painful, or infected is usually drained and healed open to keep it from coming back (recurring). In rare cases, the gland and duct are surgically removed when a cyst or infection (abscess) recurs after repeated treatments.