Those who have a habit of biting their lips may find that a small bluish bump has developed inside their mouth. It might disappear on its own or it might linger. A mucous cyst is a painless, thin sac on the inner surface of the lips. It contains clear fluid.

Mucous cysts, also known as mucoceles, are quite common in the general population, normally appearing on the lower lip. Most of the cases of mucoceles are seen in individuals under the age of 30. They are painless but can be bothersome because you are not so aware of the bumps in your mouth.

Mucous cysts are harmless. If left untreated, however, they can organize and form a permanent bump on the inner surface of the lip. They are called ranula when on the floor of the mouth, and epulis when on the gums.

Causes of mucous cysts (mucoceles)

Mucous cysts or mucoceles occur as a result of blockage or trauma to the minor salivary glands in the mouth. Once the duct of the salivary gland becomes blocked for any reason, it leads to an accumulation of a substance called sialomucin, which eventually builds and forms a tense cyst. The most common cause of a mucocele is trauma to the lower lip, likely from lip biting. They present as painless, blue swellings, typically on the lower lip, but can also occur on the upper lip, tongue and inside of the cheek.

Symptoms of mucous cysts (mucoceles)

A thin, fluid-filled sac appears on the inside of the lip. The sac is bluish and clear. It is painless, but bothersome. The sac can also occur on the tongue, palate, inside the cheeks, the floor of the mouth, or around tongue or lip piercings.

Treatment of mucous cysts (mucoceles)

Mucous cysts, because of their benign nature, generally do not require treatment. In about half of cases, the cysts will resolve on their own within one to two weeks. In some instances however, treatment is sought, mainly because the cyst becomes bothersome, interferes with normal mastication or is recurrently traumatized. If treatment is desired, there are several options, all of which should be performed in the office by a dentist.

Commonly, mucous cysts can be treated with simple incision with a medium bore needle into the cyst followed by drainage of the fluid. Mostly, this simple approach leads to complete resolution. For those cysts that persist, treatment typically involves injection of lidocaine into the area followed by excision of the upper portion of the cyst to allow the contents to drain.

Prevention of mucous cysts (mucoceles)

Unless surgically removed by a dentist, the recurrence rate of mucoceles tends to be quite high. The most important thing one can do to prevent these cysts from forming is to refrain from biting the lip, and, should one arise, see a qualified dentist.