An oral mucous cyst, or mucocele, is a benign, fluid-filled swelling that occurs when a minor salivary gland duct is damaged or blocked. Our mouth is kept moist by saliva, which is produced by three pairs of major salivary glands and hundreds of tiny, individual minor salivary glands. These minor glands are located just beneath the surface of the lining of your lips, cheeks, the roof of your mouth, and the floor of your mouth. Each of these tiny glands produces mucus (saliva) and releases it into the mouth through a small duct or tube.

A helpful analogy is to think of the inside of your lip as a lush green lawn that is kept moist by hundreds of tiny, individual sprinklers (the minor salivary glands). Each sprinkler has a delicate nozzle (the duct) that sprays a fine mist of water (saliva) onto the lawn.

• A mucocele is what happens when you accidentally step on one of these sprinkler nozzles and damage it.
• The main water line to the sprinkler is still on, but the damaged nozzle can no longer spray the water out onto the lawn.
• Instead, the water pools under the grass right at the site of the broken nozzle, creating a soft, water-filled “bubble.” This bubble of trapped saliva is a mucocele.

There are two main types of mucoceles, distinguished by how they form:

1. Mucous Extravasation Cyst: This is the most common type, accounting for over 90% of all mucoceles. It is caused by trauma (like biting your lip) that severs or tears the salivary duct. Saliva then leaks out (extravasates) into the surrounding connective tissue and gets walled off, forming the cyst. This is the “broken nozzle” in our analogy and is most common in children and young adults.
2. Mucous Retention Cyst: This type is less common and is typically seen in older adults. It is caused by a blockage of the duct, perhaps by a tiny salivary stone. The saliva backs up and dilates the duct itself, creating the cyst.

In my experience, patients often describe it as a painless, soft bump inside the mouth that suddenly appears and may burst on its own, it’s usually a mucocele.

The direct cause of a mucocele is the trauma to or blockage of a minor salivary gland duct. This disruption prevents normal saliva flow from the gland to the surface of the mouth. The saliva that continues to be produced by the gland then becomes trapped in the soft tissues, leading to the formation of the fluid-filled sac. It is a purely mechanical problem resulting from a localized injury.

Patients often don’t realize that even minor, repetitive behaviors like chewing on the lip or sucking the inside of the cheek can trigger these cysts over time.

A person develops a mucocele due to a minor, often unnoticed, injury to the inside of their mouth. The condition is not contagious, is not inherited, and is not related to any systemic disease.

The most common risk factors are activities that can cause trauma to the minor salivary glands. These include:

• Lip or Cheek Biting: A habit of biting or sucking on the lower lip or the inside of the cheek is the single most common cause.
• Accidental Trauma: An accidental bite to the lip or cheek while eating.
• Contact Sports: A blow to the face during sports can cause trauma to the oral tissues.
• Dental Appliances: Irritation or rubbing from braces or other orthodontic hardware.
• Piercings: Oral piercings can sometimes damage salivary gland ducts.

Mucoceles are most frequently seen in children, adolescents, and young adults, typically between the ages of 10 and 30, as this is the population most prone to minor oral trauma from habits or sports.

In my experience, most mucoceles develop after minor trauma that disrupts normal saliva flow especially in people with habits like lip biting or dental appliance irritation.

The signs and symptoms of a mucocele are very characteristic.

• Appearance: The classic presentation is a soft, movable, dome-shaped bump (papule or nodule). The surface is often smooth and shiny.
• Color: The cyst is typically translucent and may have a clear, bluish, or pinkish hue, depending on how deep it is located beneath the surface.
• Size: Most mucoceles are small, usually ranging from a few millimeters to about 1 centimeter in diameter.
• Contents: If the cyst ruptures, a thick, sticky, clear fluid will be released.

Location

By far, the most common location for a mucocele is the inner surface of the lower lip. This area is the most susceptible to being accidentally bitten. Other, less common locations include the inside of the cheeks, the floor of the mouth, and the underside of the tongue. A larger mucocele that occurs specifically on the floor of the mouth is given a special name, a ranula, because its appearance is said to resemble a frog’s belly.

Symptoms

In almost all cases, mucoceles are completely painless. The primary symptom is simply the awareness of a soft, fluid-filled bump in the mouth. They can be annoying, as you might find yourself constantly touching it with your tongue.

A common feature of mucoceles is that they can fluctuate in size. They may rupture on their own (often from another minor trauma), release their fluid, seem to disappear, and then gradually reform over a few weeks as the damaged gland continues to produce saliva.

Patients usually report a smooth, bluish or translucent bump that’s soft to touch, it may grow, rupture, and then refill, which can be frustrating.

A mucocele diagnosis is almost always made clinically by a dentist or a physician. An experienced provider can confidently diagnose the condition based on three key factors:

1. The characteristic appearance of a soft, bluish, translucent, fluid-filled dome on the lower lip.
2. The classic location on the inner lower lip.
3. The patient’s history, which often includes a habit of lip biting or a specific memory of biting their lip in that spot.

For a classic, straightforward mucocele, no further tests are necessary.

When is a Biopsy Needed?

If a lesion in the mouth has an unusual appearance, for example, if it is very firm, has a white or ulcerated surface, is in an atypical location, or is seen in an older adult, a doctor or dentist will recommend a biopsy. A biopsy is the definitive way to rule out other, more serious conditions. This involves surgically removing the lesion and sending it to a pathologist for examination under a microscope. This is done not because a mucocele is dangerous, but to ensure that the lesion is not something else.

Clinically, I diagnose it based on appearance and location, biopsy is rarely needed unless it’s unusually large, recurrent, or suspicious for other lesions.

The treatment for a mucocele depends on its size, location, and whether it is causing any problems for the patient.

1. Observation

For many small, superficial mucoceles, a doctor or dentist may recommend simply observing it for a few weeks. Many of these cysts will spontaneously rupture, drain, and heal on their own without any intervention.

2. The Dangers of Home Treatment

You should never try to pop, pierce, or drain a mucocele yourself. This is not a pimple. Attempting to drain it at home with an unsterile object can introduce bacteria into the area, leading to an infection. Furthermore, because you are only draining the fluid and not addressing the damaged gland that is producing it, the mucocele will almost certainly recur.

3. Surgical Excision (The Definitive Treatment) 

For mucoceles that are persistent, recurrent, large, or bothersome to the patient, the definitive treatment is a simple surgical excision.

• The Procedure: This is a minor surgical procedure that is easily performed in a dentist’s or dermatologist’s office using local anesthesia to numb the area.
• The provider will make a small incision over the cyst and will carefully dissect out and remove the entire fluid-filled sac.
• Crucially, the provider will also identify and remove the small, damaged minor salivary gland that was feeding the mucocele. Removing the associated gland is the key to preventing the cyst from coming back.
• The small incision is then typically closed with a few dissolvable stitches.
• The procedure is quick, healing is usually fast, and the recurrence rate is very low when the gland is also removed.

4. Other Removal Techniques

In some cases, other methods can be used to destroy the cyst, such as CO2 laser ablation or cryotherapy (freezing). Simple surgical excision remains the most common and reliable treatment.

Clinically, I always advise patients to avoid further trauma and monitor for recurrence especially if the original irritant like braces or biting persists.

Discovering a new lump in your mouth can be an unnerving experience, but it is reassuring to know that one of the most common causes, the oral mucous cyst or mucocele, is completely harmless. These small, saliva-filled bubbles are a simple mechanical problem, usually caused by minor trauma like biting your lip. They are not cancerous, not contagious, and are often asymptomatic. While many will go away on their own, persistent mucoceles can be permanently cured with a quick and simple surgical procedure performed by a dentist or doctor. In my experience, patients feel relieved once they understand mucoceles are benign and treatable, many are anxious at first, thinking it might be something serious.

American Academy of Oral Medicine. (2022). Mucocele. Retrieved from https://www.aaom.com/index.php?option=com_content&view=article&id=113:mucocele&catid=22:patient-condition-information&Itemid=120

The Cleveland Clinic. (2022). Mucocele. Retrieved from https://my.clevelandclinic.org/health/diseases/22956-mucocele

DermNet NZ. (n.d.). Mucocele. Retrieved from https://dermnetnz.org/topics/mucocele