A soft, painless, bluish bump on the inside of your lip, especially after you’ve bitten it, is often a mucous cyst. MedlinePlus, from the National Library of Medicine, describes an oral mucous cyst as a thin sac of clear fluid on the inner surface of the mouth. Most are harmless and burst on their own, but some need removal, and any new mouth lump deserves a look.
Two main types
MedlinePlus says mucous cysts most often appear near the openings of salivary glands (ducts).
Mucocele
Found on the inner upper or lower lip, inside the cheeks or under the tongue. Mucoceles are often caused by lip biting, lip sucking or other trauma. They are:
- usually painless but bothersome
- often clear, bluish or pink, soft, smooth, round and dome-shaped
- up to about 1 centimeter (0.39 inch) across
- able to break open on their own, but may come back
Ranula
Found on the floor of the mouth and caused by blockage of the salivary glands under the tongue. MedlinePlus describes usually painless, bluish, dome-shaped swelling below the tongue. A large ranula can affect chewing, swallowing and talking.
Emergency: if a ranula grows into the neck muscles, it can narrow the airway and impair breathing. MedlinePlus calls this a medical emergency. Call 911 or your local emergency number.
Diagnosis
A provider can usually diagnose a mucocele or ranula by looking at it. MedlinePlus says other tests may include a biopsy, ultrasound or CT scan, usually for a ranula that has grown into the neck.
Treatment
MedlinePlus says a mucous cyst often can be left alone and usually ruptures on its own. If it keeps returning, it may need to be removed.
- Mucocele: freezing (cryotherapy), laser treatment or surgery to cut it out.
- Ranula: usually removed with a laser or surgery. Typically the best approach removes both the cyst and the gland that caused it.
Don’t try to open the sac yourself, which risks infection and tissue damage. MedlinePlus says oral surgeons and some dentists can remove it. See dental specialists explained.
Possible complications
The cyst can return, and nearby tissue can be injured during removal (MedlinePlus).
When to contact a provider
MedlinePlus advises contacting your provider if you notice a cyst or mass in your mouth, or have difficulty swallowing or talking. These may be signs of a more serious problem, such as mouth cancer. See our oral cancer screening guide.
Prevention
Avoiding intentionally sucking the cheeks or biting the lips may help prevent some mucoceles.
How it differs from other bumps
For other common mouth sores, see canker sores vs cold sores. If you’re not sure what a bump is, have it checked.
Frequently asked questions
Will a mucocele go away on its own?
Often. MedlinePlus says it usually ruptures on its own but may recur.
Can I pop it?
No. MedlinePlus advises against opening the sac yourself.
Sources
By the Dentist Review Editorial Team.
This article is for general information only and is not medical advice. Talk to a licensed dentist about your own situation. See our disclaimer.
Featured image: “Close up man lips” by Kajoovi, via Wikimedia Commons, licensed CC BY-SA 4.0. Resized and compressed for the web.
Our guides are written and reviewed by the Dentist Review editorial team. We research each topic using public, authoritative sources such as the CDC, the National Institutes of Health (NIH/NIDCR), the American Dental Association (ADA) and CMS, and we update guides when guidance changes. Guides are for general information only and are not dental or medical advice; please read our disclaimer and learn more about us.