What does this mean?
Hundreds of small salivary glands sit beneath the lining of the lips, cheeks and palate, and each opens onto the surface through a duct as fine as a hair. Biting your lip, catching it on a sharp edge of a tooth or sucking on the lip constantly can crush or tear one of those ducts. The saliva cannot reach the surface, collects in the tissue around it and lifts the lining into a dome. The most common place for it is the inner surface of the lower lip; it is usually painless and soft, and it moves when you push it with your tongue.
What separates this bubble from other blisters in the mouth is its story: it fills and it empties. It grows over a few days, goes down on its own or when it is popped, then refills in exactly the same spot within a week or two. That cycle is the telling part. In conditions caused by a virus, the blisters come in clusters, they burn, they crust over within a few days and they do not refill. An allergic swelling is not a single dome but a puffiness spreading over a wide area with no clear border. A one-sided, bluish swelling under the tongue that grows large enough to lift the floor of the mouth may come from a larger gland and follows a different path.
A bubble that has been filling and emptying for weeks is not usually expected to disappear entirely on its own, because the gland leaking the saliva is still there. That is why, when it is dealt with, the contents are not simply drained; the small leaking gland is removed along with them. Where only the fluid is drained, the same picture is expected to come back. It is also not possible to tell what the bubble is by looking at the fluid inside it; the tissue that is removed is sent for examination.
Most fluid-filled bubbles in the mouth are explained by a damaged salivary duct; large, one-sided swellings under the tongue, however, form by a different route. The headings below separate these two stories.
Likely causes
What helps at home?
- Do not pop the bubble with a needle, your nail or your tooth; even if it empties, the source stays where it is, so it most often refills, and the opened surface can become infected.
- Try to notice whether you have a habit of biting or sucking your lip, or of worrying at the spot with your tongue; these habits are the most common reason it keeps coming back.
- Note how many days it takes to swell, whether it bursts, and how long it takes to come back; this cycle is directly useful at the examination.
- If you think there is a sharp edge of a tooth or a denture edge in the same area, do not try to file it down yourself, mention it at the examination; the recurrence cannot be prevented until the rubbing is removed.
- The swelling is growing quickly and makes it harder to move your tongue or to swallow.
- The swelling under your tongue has grown large enough to lift the floor of your mouth.
- The skin over the swelling has turned red, hot and painful, or a fever has come with it.
- The swelling is firm rather than soft and cannot be moved with a finger.
- The area under your jaw also swells while you eat and goes down once you finish.
Frequently asked questions
- Will it go away on its own?
- Some small, newly formed bubbles empty and never refill. With a bubble that has been filling and emptying for weeks, however, complete recovery on its own is not usually expected; as long as the gland leaking the saliva stays where it is, it may come back. Time passing is not a reason to put off the examination.
- Is there any harm in popping it?
- Popping it usually causes no serious problem, but it does not help either; the bubble refills in the same spot. Repeated popping and healing can also leave hardened tissue in the area, which can make any later procedure more difficult. Infection developing through the opened surface is possible too.
- Why does it always come back in the same place?
- Because the damaged duct and the small gland attached to it stay there. Every time the duct tries to repair itself, the saliva escapes into the surrounding tissue again. Add a habit or a sharp edge of a tooth that keeps injuring that spot, and the cycle carries on. To stop it repeating, both the gland and whatever is injuring it are looked at.
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.