Dr. Zaineb Makhzoumi is assistant professor of dermatology at the University of Maryland School of Medicine.
Dr. Zaineb Makhzoumi is assistant professor of dermatology at the University of Maryland School of Medicine. (Courtesy of University of Maryland, Baltimore Sun)

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. Dr. Zaineb Hassan Makhzoumi, an assistant professor of dermatology at the University of Maryland School of Medicine, said they are more annoying than dangerous. But those who suffer from them may want to have them removed by a doctor.

How common are mucous cysts, and why do they form?


Mucous cysts, also known as mucoceles, are quite common in the general population, usually occurring on the lower lip. The majority of cases (70 percent) occur in individuals under the age of 30. They 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. These cysts generally vary in size from 2 to 10 millimeters in diameter and often have a bluish hue to them. 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.

How do you know if it's a harmless cyst or something more serious?

Annoying as they can be, the good news is that mucoceles are harmless, with no risk of transformation into skin cancer. Rarely, the cyst can rupture into the tissue of the lip, causing inflammation and granuloma formation, which ultimately results in scarring; however these cases represent a minority. There are many other lesions that can develop in the oral cavity, especially on the lip, and any cyst or lesion that persists for more than two months, or any lesion that is painful or bleeds, should be evaluated promptly by a physician.

Can the cysts be ignored or treated at home?

Mucous cysts, because of their benign nature, generally do not require treatment by a physician. 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 physician.

What are the treatment options, and are there potential complications from them?

Most commonly, these cysts can be treated with simple incision with a medium bore needle into the cyst followed by drainage of the fluid. Most of the time, 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. This is followed by electrodessication (application of high-frequency electric current) to the remaining cyst lining. These wounds are left to heal on their own and do so in about two to four days. In younger children with these cysts, the approach usually involves applying lidocaine jelly followed by placing one suture in the middle of the cyst and leaving it in place for one week, which causes the cyst to regress.

If you've had one are you prone to new ones and can you prevent them?

Unless surgically removed by a physician, the recurrence rate of mucoceles tends to be quite high, around 70 to 80 percent. Lesions tend to recur periodically, and individuals who have had one can expect to develop more over time. With adequate surgical treatment, however, the recurrence rate drops to 10 percent. 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 dermatologist for treatment options.