A small, clear bump appearing suddenly on the inside of the lip is a common and usually harmless occurrence. This lesion is most frequently located on the inner surface of the lower lip, a location often subject to minor trauma. These lesions are among the most common non-cancerous growths of the oral cavity.
Identifying the Mucous Retention Cyst
The small, fluid-filled swelling is most likely an oral mucocele, often called a mucous retention cyst or mucous extravasation phenomenon. It is a benign, dome-shaped lesion that is movable and generally painless, unless it interferes with chewing or speaking. Mucoceles are a common salivary gland disorder.
The mucocele often presents with a bluish or translucent color because the accumulated mucus is visible just beneath the mucosal surface. Their size can vary from a few millimeters to a couple of centimeters wide. The two main types are the extravasation type, resulting from a tear, and the retention type, resulting from a blocked duct. The extravasation type is the most common, seen on the lower lip, and is technically not a true cyst because it lacks an epithelial lining.
The Mechanism of Formation
Mucocele formation is directly related to the numerous minor salivary glands embedded just below the lining of the lip. These glands continuously produce mucus, which travels through small ducts to lubricate the oral surface. The problem begins when one of these ducts is damaged or blocked, disrupting the normal flow of mucus.
The overwhelming cause is localized trauma, most frequently from accidentally biting the lip or from habitual lip-sucking. This mechanical injury causes the duct of a minor salivary gland to rupture.
When the duct breaks, the mucus leaks out (extravasates) into the surrounding connective tissue instead of flowing into the mouth. This pooling of mucus creates an inflammatory response, resulting in the visible, fluid-filled swelling.
Approaches to Management
For the majority of small mucoceles, active treatment is unnecessary because they resolve on their own. Many lesions will spontaneously rupture, drain the fluid, and flatten out, typically within three to six weeks.
Conservative management is the best approach during this time, meaning avoiding any action that could irritate or re-injure the area. Focus on stopping habits like lip-biting or sucking, which can prevent healing or cause recurrence.
Avoid attempting to “pop” or drain the bump at home. This risks introducing bacteria and secondary infection, and the mucocele usually reforms quickly since the damaged gland is still producing mucus.
If the lesion persists, is large, or causes discomfort, professional intervention may be needed. Treatment options include surgical excision, where the lesion and the associated minor salivary gland are removed to prevent recurrence. Other methods involve cryotherapy or laser ablation.
Signs Requiring Medical Evaluation
While most small bumps on the lip are benign mucoceles that resolve naturally, specific signs indicate the need for a professional medical evaluation. Seek an assessment if the lesion does not improve or persists for several weeks, or if it is rapidly increasing in size or continues to recur immediately after draining.
Evaluation is also important if the bump is painful, firm to the touch, or feels fixed and non-movable within the lip tissue. Other types of oral lesions can sometimes mimic a mucocele, including a benign growth like a fibroma or, infrequently, a tumor of the minor salivary glands. A professional examination allows for an accurate diagnosis and rules out more serious conditions, ensuring appropriate care.