A swollen jaw on one side signals an underlying health issue in the structures of the mouth, face, or neck. This unilateral swelling, known medically as facial or mandibular edema, occurs when fluid accumulates in the tissues of one cheek, the jawline, or beneath the chin. The cause can range from a minor localized issue to a serious infection, indicating the body is reacting to inflammation, trauma, or disease. Understanding the potential sources of this swelling is the first step toward appropriate care.
Causes Originating from Teeth and Gums
Infections stemming from the teeth and gums are the most frequent causes of sudden, unilateral jaw swelling. A dental abscess is a localized pocket of pus that forms at the root tip (periapical) or in the surrounding gum tissue (periodontal). Bacteria enter the inner tooth through a deep cavity or crack, spreading to the bone and causing painful, firm swelling that can track down the jawline.
Pericoronitis is another localized cause, involving inflammation of the gum tissue surrounding a partially erupted tooth, usually a wisdom tooth. Food debris and bacteria become trapped under the tissue flap (operculum), leading to infection and swelling often accompanied by difficulty opening the mouth. Severe gum disease (periodontitis) can also cause abscess formation and localized swelling as the infection destroys supporting bone and soft tissue. Post-extraction complications, such as an infected socket, introduce another potential source of localized infection that can manifest as unilateral swelling near the surgical site.
Swelling Related to Glands and Lymph Nodes
Swelling not tied to the teeth often originates in the salivary glands or regional lymph nodes. The three major salivary glands—parotid, submandibular, and sublingual—can become inflamed, a condition called sialadenitis. This inflammation most commonly affects the parotid gland (in front of the ear) or the submandibular gland (under the jaw).
Acute bacterial sialadenitis presents with rapid-onset pain and swelling, often due to diminished salivary flow or obstruction. Salivary stones (sialoliths) are calcium deposits that can block the salivary duct, leading to a backup of saliva and subsequent glandular swelling, which is often episodic and increases during eating. The lymph nodes along the jawline and neck may also swell (lymphadenopathy) as a response to local or systemic infection, such as an upper respiratory infection or a dental infection. Lymph node swelling is generally softer and more mobile than the firm, fixed swelling of a dental abscess or major salivary gland issue.
Musculoskeletal and Injury-Related Causes
Swelling can also result from the jaw’s mechanics and trauma, though often less dramatically than infection. Temporomandibular Joint (TMJ) disorders, which affect the hinge connecting the jawbone to the skull, can cause unilateral facial swelling. This is typically due to inflammation within the joint capsule (capsulitis) or synovial tissue (synovitis), often presenting as pain and limited jaw movement. Localized swelling may be seen, particularly in cases of inflammatory arthritis affecting the joint.
Muscle strain, such as from chronic clenching or grinding of the teeth (bruxism), can lead to hypertrophy of the masseter muscle, which may be perceived as firm, unilateral fullness along the angle of the jaw. Direct trauma to the face or jaw, such as from a fall or sports injury, causes immediate swelling from deep bruising or the physical damage of a fracture. This swelling is the body’s immediate inflammatory response to physical damage, typically appearing rapidly and accompanied by tenderness and discoloration.
Identifying Urgent Symptoms
While many causes of unilateral jaw swelling can be treated by a dentist or general practitioner, certain symptoms require immediate emergency medical attention. Swelling that rapidly progresses or begins to interfere with the ability to breathe or swallow is a medical emergency, as this suggests the infection is spreading into the deep spaces of the neck. Rapid spread, especially when accompanied by a high fever, severe chills, or mental confusion, can be life-threatening and may indicate a severe condition like Ludwig’s angina.
Sudden difficulty opening the mouth, known as trismus, should also be evaluated urgently, as it can signal a severe infection that is irritating the muscles responsible for jaw movement. Swelling that spreads to the eye area or down the neck, or is accompanied by a change in vision, represents a serious infection that is moving beyond localized control. If these red flag symptoms appear, proceed directly to an emergency room to ensure the infection is contained and treated with intravenous antibiotics or surgical intervention if necessary.