A tooth infection can cause lymph nodes to swell. Lymph nodes are small, bean-shaped organs that are part of the lymphatic system, which filters out harmful substances like bacteria and viruses. When bacteria from an untreated dental infection spread beyond the tooth, nearby lymph nodes activate to contain the threat. This immune response causes them to become enlarged and tender, signaling that the body is actively fighting a localized infection in the oral cavity or jaw area.
The Immune Connection: Why Nodes Swell
When a tooth infection takes hold, the immune system immediately responds to the invading bacteria. The lymphatic system acts as a drainage network, and the lymph nodes function as filters that intercept infectious material from surrounding tissues. Bacteria and inflammatory substances from the infected tooth travel through lymphatic vessels and are delivered to the nearest lymph nodes.
The physical swelling happens because the nodes become a battleground. Inside the node, trapped bacteria are confronted by specialized white blood cells, called lymphocytes, and other immune cells. These immune cells rapidly multiply within the node’s tissue to mount an effective defense. This sudden increase in cellular volume causes the node to physically enlarge and become noticeable as a lump.
This enlargement is a direct, localized sign that the infection has progressed enough to trigger a regional immune response. The resulting swelling often feels tender or sore to the touch because of the intense immune activity occurring inside the node. The nodes are acting as a barrier, attempting to destroy the pathogens before they can spread further into the bloodstream.
Identifying the Affected Lymph Nodes
The location of the swollen nodes provides a direct clue about the source of the infection, as lymphatic drainage follows specific pathways from the mouth and face. A tooth infection typically causes swelling in the nodes closest to the problem site.
Common Node Locations
For infections in the lower teeth, the submandibular nodes (beneath the jawbone) and the submental nodes (under the chin) are most commonly affected. Infections from the back teeth often drain toward the upper deep cervical nodes, which run along the sides of the neck.
You can check for these nodes by feeling for small, mobile lumps in these areas. Swollen nodes due to a dental infection are typically soft, tender, and somewhat movable under the skin, especially on the same side as the infected tooth.
Warning Signs and Urgent Care
Tender, mobile lymph nodes are a standard sign of a localized infection, but certain symptoms indicate the infection is spreading and requires immediate medical attention. Warning signs include nodes that become hard, fixed, or rapidly grow in size, or swelling that extends beyond the jawline into the facial tissues or under the eye. A spreading infection can also lead to systemic symptoms, such as a fever over 100.4°F or chills.
Severe symptoms occur if the infection migrates into deep tissue spaces in the neck and throat. Seek urgent care immediately if you experience difficulty swallowing, an inability to fully open your mouth, or difficulty breathing. These symptoms can signal a life-threatening condition like Ludwig’s angina, where swelling in the floor of the mouth and neck compromises the airway.
Treating the Source of the Infection
Swollen lymph nodes are a symptom, meaning they will not resolve permanently until the dental infection is eliminated. The primary focus of treatment is removing the source of the bacteria within the tooth. Treatment often begins with systemic antibiotics, which help control the spread of the infection into surrounding tissues.
Antibiotics alone are insufficient because they cannot penetrate the infected dental pulp to fully resolve the issue. Definitive treatment requires a dental procedure, such as a root canal to clean out the infected tissue, or an extraction if the tooth is too damaged. If a large abscess is present, a dentist may perform an incision and drainage to release pus and pressure. Once the source is treated, the lymph nodes will gradually return to their normal size, which can take a few days up to a couple of weeks.