A Bartholin's cyst, also called a Bartholin's duct cyst, is a small fluid-filled sac just inside the opening of a woman's vagina.

A Bartholin's cyst can stay small and painless and may not cause any symptoms. However, the cyst can become infected, which can cause a painful collection of pus (an abscess) in the Bartholin's gland.

Read more about the symptoms of a Bartholin's cyst.

What causes Bartholin's cysts?

The Bartholin's glands are a pair of pea-sized glands. They are found just behind and either side of the lips that surround the entrance to the vagina. The glands are not usually noticeable because they are rarely larger than 1cm (0.4 inches) across.

The Bartholin's glands secrete fluid that acts as a lubricant during sex. The fluid travels down tiny tubes, called ducts, into the vagina. If the ducts become blocked, they can fill with fluid and expand to form a cyst.

It's not known exactly why the ducts become blocked, but some cases have been linked to bacterial infections. Bacteria are known to sometimes infect existing cysts, causing an abscess to develop.

Read more about the causes of a Bartholin's cyst.

When to see your GP

You should always see your GP if you develop a lump in the area around your vagina. They will usually be able to diagnose a Bartholin's cyst from its appearance during a physical examination.

If your GP thinks the cyst or one of your Bartholin's glands may be infected, they may use a swab to remove a sample of discharge for analysis to identify the bacteria responsible.

In some cases your GP may also advise having a biopsy of the cyst. This involves removing a small sample of tissue so it can be examined under a microscope to check that the cyst is not a sign of a rare type of vulval cancer.

How Bartholin's cysts are treated

If you do not have any noticeable symptoms, it's unlikely you will need treatment.

If the cyst is painful, your GP may recommend some simple self-care measures, such as soaking the cyst in warm water several times a day for three or four days.

Several treatments are available to treat any pain or infection and drain the cyst if necessary. Most of these treatments involve a minor surgical procedure.

However, Bartholin's cysts are estimated to recur after treatment in about one in every five women.

Read more about treating a Bartholin's cyst.

Who is affected?

It's estimated that around 1 in every 50 women will develop a Bartholin's cyst or abscess at some point. The condition usually affects sexually active women aged 20 to 30.

The Bartholin's glands do not start functioning until puberty, so Bartholin's cysts do not usually affect children. The cysts are also uncommon after the menopause as this usually causes the Bartholin's glands to shrink.

Preventing Bartholin's cysts

As it is not clear exactly why Bartholin's cysts develop, it isn't usually possible to prevent them.

However, practicing safe sex can help reduce your chances of picking up a sexually transmitted infection (STI) such as gonorrhoea or chlamydia, which can cause an abscess to develop.

The best way to reduce your chances of developing these infections is by using a condom every time you have vaginal sex.

Read more advice about STIs.