A bump on the inner lip is a common finding, often causing concern because it is unexpected and noticeable within the sensitive oral environment. The inner lip is lined by the oral mucosa, a delicate membrane constantly exposed to minor injuries from chewing, dental work, and sharp foods. This low-level trauma makes the area prone to developing various temporary and benign lesions. Understanding the most frequent causes can help distinguish a minor issue from one that requires professional attention.
Bumps Caused by Trauma and Cysts
One of the most frequent causes of a fluid-filled bump is a mucocele, a type of mucus retention cyst. This lesion occurs when the duct of a minor salivary gland is severed or blocked, often after repeated lip biting. Mucus then leaks into the surrounding connective tissue, forming a cyst-like swelling that can range in size from a few millimeters to two centimeters wide.
A mucocele typically appears soft, painless, and dome-shaped. It often has a clear, pearly, or bluish tint due to the pooled mucus just under the surface. These lesions are moveable and most commonly develop on the inner surface of the lower lip. Although they can sometimes rupture and drain, they may also refill, making recurrence common until the underlying salivary gland is repaired or removed.
A different type of physical lump is the irritation fibroma, which consists of dense, scar-like tissue rather than fluid. This firm growth forms as a reactive response to chronic irritation, such as habitual lip biting or friction from a sharp tooth or dental appliance. An irritation fibroma presents as a firm, smooth, dome-shaped nodule that is fixed in the tissue and is usually the same color as the surrounding pink mucosa. Since this benign connective tissue does not resolve on its own, it typically requires surgical removal by a dentist or oral surgeon if it causes discomfort.
Inflammatory and Ulcerative Causes
Lesions characterized by an open sore and inflammation are distinct from the physical lumps caused by cysts and scar tissue. The most common of these are canker sores, also known as aphthous ulcers, which are painful, shallow sores that form on the soft tissues inside the mouth. These ulcers are non-contagious and typically appear with a white or yellowish center surrounded by a distinct red, inflamed border.
Minor canker sores are the most frequent type, usually measuring less than one centimeter across and healing without scarring within one to two weeks. While the exact cause is unknown, common triggers include stress, minor tissue injury from dental work, and sensitivities to acidic foods. A tingling or burning sensation often precedes the visible ulcer by a day or two, marking the beginning of the painful period that can make eating and talking difficult.
The oral mucosa can also react to direct physical damage, such as a thermal or chemical burn. Ingesting hot foods or liquids can cause the tissue on the inner lip to blister or peel, leaving a red, raw area. Strong chemical irritants, such as those in certain mouthwashes or medications, can similarly lead to localized inflammation and ulceration. These burns are temporary injuries and generally heal quickly, provided the source of irritation is removed.
When to Seek Professional Evaluation
While the majority of inner lip bumps are benign and self-limiting, certain features warrant a professional evaluation from a dentist or physician. The most important factor is duration; any lesion that persists unchanged for two weeks or longer should be examined. This time frame is a standard benchmark, as most minor irritations and ulcers heal within this period.
Other concerning signs include a bump that rapidly increases in size, exhibits unusual firmness or hardness upon palpation, or is accompanied by symptoms like numbness in the lip or difficulty swallowing. Changes in appearance, such as the development of a white or red patchy area, or spontaneous bleeding from the lesion, also indicate a need for professional assessment.
A healthcare professional will begin the evaluation with a visual examination and palpation to assess the lesion’s texture and mobility. If the diagnosis remains unclear, or if there is suspicion of a more serious condition, a biopsy may be necessary. This procedure involves taking a small tissue sample for microscopic analysis to definitively rule out malignancy or other complex pathologies. Relying on self-diagnosis for persistent or atypical growths is unsafe.