A cyst is a sac or cavity that can form anywhere inside your body or on the surface of your skin. It can be filled with fluid or pus, and may feel like a hard lump. The cells that form the outer layer of the sac are abnormal — they’re different from any others around them.

There are many different types of cysts. Though cysts can appear in connection with cancer, most cysts aren’t cancerous. A cyst is distinct from a tumor because of its enclosed sac.

An abscess is a pus-filled infection in body tissue. It’s usually caused by bacteria but can also be the result of viruses, parasites, or swallowed objects. The pus forms as your immune system mobilizes to fight the infection.

An abscess can show up on your skin, where it’s easy to see. Or it can form inside your body, where it’s harder to diagnose. A small abscess on the skin may also be called a boil or a furuncle.

While a cyst is a sac enclosed by distinct abnormal cells, an abscess is a pus-filled infection in your body caused by, for example, bacteria or fungi.

The main difference in symptoms is:

  • a cyst grows slowly and isn’t usually painful, unless it becomes enlarged
  • an abscess is painful, irritated, often red, and swollen, and the infection can cause symptoms elsewhere in the body

Both abscesses and cysts can form in many different places in your body. When an already-formed cyst becomes infected, it becomes an abscess. But an abscess doesn’t have to begin as a cyst. It can form on its own.

Here are some specific examples that help show the difference between a cyst and an abscess.

Bartholin’s cyst or abscess

The Bartholin’s glands are two pea-sized structures, one located on each side of the vaginal opening. They’re not normally visible. They secrete the fluid that lubricates the vagina.

In about 2 percent of women, the Bartholin’s glands can become blocked due to an injury or irritation. This can cause the fluid they secrete to back up, enlarging the gland. When this happens, it’s called a Bartholin’s duct cyst, Bartholin’s cyst, or bartholinitis.

Often, a Bartholin’s cyst is small and shows no symptoms. It can grow large and cause discomfort when walking, sitting, or having sexual intercourse.

Bartholin’s gland abscess is an infection of the gland or duct leading from it. The abscess can form without a cyst having been present. Or it can result from a Bartholin’s duct cyst becoming infected.

Bartholin’s abscesses are almost three times more common than Bartholin’s cysts.

The most common bacteria causing abscesses in the Bartholin’s gland are these anaerobic species:

  • Bacterioides fragilis
  • Clostridium perfringens
  • Peptostreptococcus species
  • Fusobacterium species

Sexually transmitted bacteria, such as Neisseria gonorrhoeae (which results in gonorrhea) and Chlamydia trachomatis (responsible for chlamydia infection), can also be the cause of a Bartholin’s gland abscess.

Dental cyst vs. abscess

A dental cyst is a small enclosed sac growing around your tooth. Dental cysts usually form at the roots of dead teeth or around the crowns or roots of teeth that haven’t broken through the gum. If it becomes infected, a dental cyst becomes an abscess.

Dental cysts can remain small and symptom-free. If they grow, they can cause pain by pressing against a tooth or gum.

A dental abscess is an acute infection that will be swollen and very painful. Sometimes the bacteria causing the infection will produce a bad taste in your mouth.

Common types of cyst and abscess

Some of the common types of cyst and abscess include:

The treatment of cysts and abscesses varies by their location in the body. Some cysts may require no treatment at all. Others that are causing pain or discomfort may need removal.

Abscesses are usually painful infections that must be treated to avoid the spread of the infection to other parts of your body and to reduce pain.

It may not be possible to feel or see cysts and abscesses in internal organs. They require careful testing and diagnosis. Blood testing may help to identify infection. Imaging techniques including X-ray, CT scan, and MRI scan may help doctors find the location of the cyst or abscess.

Let’s take a look at treatment of the two examples we’ve already considered:

Bartholin’s cyst or abscess

A Bartholin’s duct cyst may show no symptoms and require no treatment. If the cyst has grown large enough to cause discomfort, it may require drainage.

An abscess is infected and must be drained. If the surrounding skin has become swollen, red, and tender, it’s a sign of spreading infection (cellulitis). Cellulitis is treated with a broad-spectrum antibiotic such as:

  • cefazolin
  • cefuroxime
  • ceftriaxone
  • nafcillin
  • oxacillin

A specialized instrument called a Word catheter is the safest way to drain a Bartholin’s duct cyst or abscess. To do this, your doctor makes a small incision next to the gland and inserts the Word catheter into the cyst or abscess.

The catheter has a tiny balloon at the end that keeps it inside the gland. A small tube leading from the balloon allows the pus or fluid to drain from the Bartholin’s gland.

You’ll have a local anesthetic for the procedure.

Dental cyst or abscess

A dental cyst may show no symptoms, but an abscess is very painful and requires immediate attention from a dentist.

If the cyst is at the end of a dead root, a root canal treatment might allow the cyst to repair itself. A small cyst that’s causing problems can sometimes be removed along with the affected tooth.

A dental abscess often occurs along with tooth decay. It can be caused by a broken or chipped tooth. The breaks in the enamel of the tooth allow bacteria to enter and infect the living tissue at the center of the tooth known as pulp.

Antibiotics for dental abscess include:

  • amoxicillin
  • clindamycin
  • metronidazole

A lump or swelling anywhere on your body should be checked by a doctor or dentist.

If there’s also redness and pain, it’s a sign there may be infection. You should see a doctor or dentist soon.

Some cysts are small and show no symptoms. You may not even be aware of them. But cysts that grow larger may to produce problems and sometimes lead to infection or abscess.

An abscess is an acute infection and requires immediate medical attention.