A mucous cyst, also known as a mucocoele, is a fluid-filled swelling that occurs on the lip or the mouth.
The cyst develops when mucus from the mouth’s salivary glands becomes plugged. Most cysts are on the lower lip but can occur anywhere inside the oral cavity. Most cysts are temporary and painless. However, cysts can become permanent if they are not treated.
Mucous cysts are most commonly caused by trauma to the oral cavity, such as:
- lip biting (most common cause)
- accidental rupture of salivary gland
- adjacent teeth causing chronic damage
- cheek biting
Poor dental hygiene and a habit of lip or cheek biting due to stress can also put you at higher risk for developing mucous cysts.
The symptoms of a mucous cyst vary by how deep the cyst lies within the skin and how often lip cysts occur. Most cysts are not painful, but they can be bothersome. Frequent cysts can become painful over time.
Symptoms of superficial (close to the surface of the skin) cysts:
- raised swelling
- bluish color
- soft to the touch
- lesions less than 1 cm in diameter
Symptoms of cysts deeper within the skin include:
- more nodule (appears more like a rounded bump)
- whitish color
- tender to the touch
Doctors rely on clinical symptoms for diagnosis. Your doctor may also ask about a history of trauma associated with lip biting to make an accurate diagnosis.
In certain cases, a biopsy of the cyst may be required to make a positive diagnosis. During this a small tissue sample will be removed. The tissue will be microscopically examined. By looking at the cells, doctors can decide if the cyst is cancerous or not.
Doctors may require a biopsy in cases where:
- the mucous cyst is larger than 2cm
- the cyst’s appearance suggests adenoma (cancer) or lipoma
- there is no history of trauma
Treatment is based upon the severity of the mucous cyst. Sometimes cysts may not require treatment and will heal on their own over time. Superficial cysts often resolve spontaneously. To prevent infection or tissue damage, do not try to open or remove cysts at home. Frequent or recurring cysts may require further medical treatment.
Treatments used in mucous cysts that are not very severe include:
- laser therapy: a small, directed beam of light is used to remove the cyst
- cryotherapy: the cyst is removed by freezing
- intralesional corticosteroid injection: a small needle injects a steroid into the cyst to reduce inflammation and accelerate healing
To prevent recurrence—or to treat especially severe cysts—your doctor may recommend surgical removal of the cyst or even the complete salivary gland.
Mucous cysts can take anywhere from a week to two years after treatment to heal, depending on the type and severity of the cyst. Even after healing, the only way to ensure a cyst will not come back is to have it surgically removed. Avoid habits like lip or cheek biting to help prevent future cysts.