What is it?
As well as the major salivary glands, there are hundreds of minor salivary glands in the lips, the cheeks, the palate and under the tongue. What these glands produce reaches the surface of the lining of the mouth through fine ducts. When a duct is damaged or blocked, the saliva cannot get to the surface and collects within the surrounding tissue. The soft swelling that results is called a mucocele.
It is seen most often on the inner surface of the lower lip, because this is the area most open to being bitten. The typical appearance is a bluish or see-through, dome-shaped bubble that is painless and feels soft when it is pressed. Its size ranges from a few millimetres to a centimetre. Those close to the surface look clear and tense, while deeper ones are the colour of the surrounding lining.
A mucocele is not a tumour, it is not treated as a malignant condition and it is not infectious. What sets it apart is how it behaves: it opens on its own or with a bite, the thick fluid inside drains out, it stays flat for a few days and then fills again. This cycle repeats because the connection with the gland it comes from is still there.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
Biting the lip and mechanical damage
This is the most common cause. Biting the inside of the lower lip absent-mindedly, or out of habit, can tear the duct of a small gland. This habit is also why it is seen so often in children and young people.
- 02
Sharp tooth edges and appliances
The sharp edge of a broken tooth, an ill-fitting denture or the area rubbed by orthodontic wires can damage the lining of the mouth again and again. Mucoceles that keep coming back in the same area most often point to a source like this.
- 03
Blockage of the duct
In a less common form, the saliva builds up inside the duct and widens it. In this form the swelling is walled by the duct itself; although it looks similar, the way it forms is different and this can affect the treatment decision.
- 04
The form arising from the gland under the tongue
The form arising from the major gland under the tongue is called a ranula. It sits on the floor of the mouth, most often to one side of the midline, and can be noticeably larger than mucoceles on the lip.
How does it progress?
- Superficial
The form just under the lining
It looks small, clear and tense. It opens and drains easily, which is why it is often thought to have settled on its own. It can be expected to appear again at the same spot.
- Inside the lip
The most common site
On the inner surface of the lower lip there is a soft, painless bubble that is bluish or the colour of the surrounding lining. It can catch between the teeth while you speak and eat, which damages it again.
- Ranula
The form on the floor of the mouth
It arises from the gland under the tongue. It is larger, it can push the tongue upwards and it can affect speech and swallowing. Assessing and treating it is different from a mucocele on the lip.
- Recurring
The form that drains and fills again
It opens on its own or with a bite, goes flat, and fills again a few days later. The cycle carrying on shows that the connection with the gland is still there and brings the need for a procedure into consideration.
How is it treated?
In a mucocele that has only just appeared and is small, a short period of monitoring may be used; some settle on their own within a few weeks. During that time you are asked not to bite the area and not to try to drain the swelling with a needle or by squeezing it. Draining it yourself eases the trouble for a while; because it does not remove the gland it comes from, it does not stop it coming back and it brings a risk of infection.
The approach used for mucoceles that do not settle or that keep coming back is to remove the lesion together with the small salivary gland that feeds it. The procedure is carried out under local anaesthetic and the tissue that is removed is sent for examination. Draining the contents alone, or removing only part of the lesion, can lead to it forming again in the same area. Sources of damage such as a biting habit and a sharp tooth edge are dealt with in the same process.
A ranula on the floor of the mouth, and swellings that are unusually large or growing quickly, are assessed by oral and maxillofacial surgery; imaging may be needed in this picture and the options are different. It is also kept in mind that not every bubble in the mouth is a mucocele. Because a salivary stone, growths arising from blood vessels and other soft tissue lesions can look similar, the diagnosis is made by examination.
- If the swelling is growing quickly, becoming firm or changing colour
- If a swelling on the floor of the mouth is pushing your tongue up, or making swallowing or speaking difficult
- If signs of infection such as pain, redness and discharge have been added in the area
- If the swelling has not got smaller for three weeks and its surface has turned into a sore that will not heal
How is it prevented?
- If you have a habit of biting the inside of your lip or cheek, try to notice it and cut it down.
- Have broken or sharp tooth edges and ill-fitting dentures put right.
- Do not try to burst the swelling with a needle, your fingernail or anything else.
- Do not just keep an eye on bubbles that come back in the same area; there is a reason for the recurrence.
Frequently asked questions
- If I burst the bubble, will it go?
- Bursting it lets the fluid out and the swelling stays flat for a few days. But because the small gland producing the saliva and the damaged duct are still in place, it can be expected to fill again at the same spot. What is more, going at it with anything that is not clean carries a risk of infection and of damage to the tissue. It is better for a bubble that keeps coming back to be assessed at an examination.
- Does a mucocele go away on its own?
- Some of those that have newly formed and are small can settle on their own within a few weeks; this is seen particularly in ones close to the surface. On the other hand, in a lesion that has been there for months, that drains and fills again, or that is steadily getting bigger, there is less to be gained from waiting. It is best to decide on the period of monitoring together with your dentist after an examination.
- Can it come back after it is removed?
- When the lesion is removed together with the small gland it comes from, it would not be expected to come back at the same spot. Even so, if the habit of biting the lip carries on, or a sharp edge that damages the lining of the mouth has not been dealt with, a new mucocele can develop from a neighbouring gland. That is why removing the source of the damage matters as much as the procedure itself.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.