The appearance of a bump underneath the lip can be a source of concern. Bumps in this area, known as the perioral region, can originate from different tissues, including fluid-filled sacs, inflamed skin structures, or an overgrowth of underlying connective tissue. Understanding the specific characteristics of these bumps, such as their texture, color, and location, helps to identify their likely origin. Most bumps in this location are temporary and resolve without intervention, but distinguishing features indicate when a professional evaluation is necessary.
Bumps Caused by Mucus and Saliva Retention
One of the most frequent causes of a bump on the inner surface of the lower lip is a mucocele, a fluid-filled sac resulting from minor salivary gland dysfunction. These lesions form when the delicate duct of a salivary gland is severed or ruptured, often due to minor trauma like biting or sucking on the lip. The mucus then spills into the surrounding connective tissue, creating a cyst-like swelling.
A typical mucocele appears as a soft, dome-shaped bubble that is often translucent, clear, or slightly bluish due to the fluid lying close to the surface. It is usually painless and mobile, ranging in size from a few millimeters up to two centimeters. They develop specifically on the inner aspect of the lower lip.
These cysts may spontaneously rupture and drain, often while eating, which leads to temporary resolution. However, they frequently recur because the damaged salivary gland duct continues to leak mucus into the tissue. A ranula is a related, but less common, type of mucocele that is typically larger and found on the floor of the mouth, usually involving the major sublingual salivary glands.
Inflammatory and Infectious Skin Causes
Bumps located on the skin portion of the lip often arise from inflammatory or infectious processes. Acne and folliculitis result from the blockage and inflammation of hair follicles or sebaceous glands beneath the skin. These appear as red, tender papules or pustules, often with a white or yellow tip from the buildup of pus and sebum.
Folliculitis, an infection of the hair follicle, can mimic acne and is common in the chin and jawline area just under the lip. These bumps may be itchy or painful and can spread if the infection moves to nearby follicles.
A cold sore, caused by the Herpes Simplex Virus type 1 (HSV-1), is a distinct infectious bump preceded by a characteristic tingling, itching, or burning sensation. A cluster of small, painful, fluid-filled blisters emerges, typically along the border of the lip. The blisters eventually merge, break open, and crust over, usually healing completely within two to three weeks.
Contact dermatitis results from an allergic reaction or irritation from a substance touching the skin. This can manifest as a rash, redness, scaling, or cracking on the lips or the surrounding skin, sometimes accompanied by a burning or stinging sensation. Common triggers include ingredients in lip balms, lipsticks, toothpastes, or excessive lip licking.
Benign Tissue Growths
Solid, non-fluid-filled lumps under the lip often represent a benign overgrowth of normal tissue components. A traumatic fibroma presents as a firm, smooth, dome-shaped nodule. This growth is a dense mass of connective tissue that forms as a reactive response to chronic irritation, such as repeated biting of the inner lip.
Fibromas are typically the same color as the surrounding mucosa, are painless, and develop slowly. Unlike a mucocele, which is soft and fluid-filled, the fibroma is hard and fixed due to its fibrous composition, often reaching about one centimeter in size.
Another type of solid lump is a lipoma, a slow-growing collection of mature fat cells located just beneath the skin layer. When palpated, a lipoma feels soft and rubbery and is usually easily movable. While rare on the lip, it is a benign tumor that is asymptomatic unless it grows large enough to interfere with movement or press on a nerve.
An epidermoid cyst is a slow-growing, firm lump that develops when surface skin cells become trapped beneath the skin and multiply, creating a sac filled with keratin debris. These cysts are often mobile and may have a central dark spot, though they are less common in the lip area than on the face or neck. The contents of the cyst are a thick, cheesy substance.
Signs That Require Medical Consultation
While most bumps under the lip are harmless and self-limiting, certain signs warrant prompt medical evaluation by a dentist or dermatologist. Any bump that is firm, fixed, or hard to the touch and does not move easily should be assessed. A bump that bleeds easily, especially without injury, or one that develops an open, ulcerated sore and does not heal after two to three weeks requires attention.
Rapid changes in the size, shape, or color of a lesion over a short period are concerning. Other signs include any lump associated with numbness, persistent pain, or difficulty with eating, speaking, or swallowing. Seeking consultation for any persistent or unusual growth ensures an accurate diagnosis.