Allergies can cause lymph nodes to swell, though this reaction is usually mild and localized. While infections are a more frequent cause, an allergic response involves the immune system, which can lead to some enlargement of these glands. The swelling is typically temporary and resolves once the allergen is no longer present or the allergic reaction is controlled.
The Role of Lymph Nodes
Lymph nodes are small, bean-shaped structures integral to the body’s lymphatic system and immune system. They are distributed throughout the body, with clusters in the neck, armpits, groin, chest, and abdomen. Their primary function involves filtering lymph fluid, trapping foreign substances such as bacteria, viruses, and damaged cells. They house immune cells that detect and combat these threats, initiating a protective immune response.
How Allergies Affect Lymph Nodes
When an individual encounters an allergen, such as pollen or pet dander, their immune system may mistakenly identify this harmless substance as a threat. This triggers an immune response, releasing chemicals like histamine that cause inflammation. This inflammation can extend to nearby lymph nodes, causing them to swell as they become active. Allergic lymph node swelling is typically mild and localized to the area near the reaction. For example, seasonal allergies or sinus issues might cause nodes in the neck or under the jaw to enlarge. While a direct allergic reaction can stimulate lymph nodes, allergies can also weaken the immune system, potentially making the body more susceptible to secondary infections that then cause more pronounced swelling.
Other Reasons for Swollen Lymph Nodes
Swollen lymph nodes most commonly indicate the immune system is actively fighting an infection. Viral infections like the common cold, flu, strep throat, and mononucleosis are frequent culprits, often causing neck swelling. Bacterial infections, such as a skin wound or an abscessed tooth, can also lead to localized lymphadenopathy. The nodes typically become tender and firmer when reacting to an infection. Beyond infections, other conditions can also cause lymph nodes to swell. Autoimmune diseases, such as lupus or rheumatoid arthritis, can trigger widespread lymph node enlargement. In rarer instances, swollen lymph nodes can be a sign of certain cancers, including lymphoma or leukemia, or indicate cancer has spread from another part of the body. Unlike infection-related swelling, cancerous lymph nodes might feel hard, fixed, and often painless.
When to Consult a Doctor
While allergies can cause mild lymph node swelling, certain characteristics warrant medical evaluation. Consult a healthcare professional if swollen lymph nodes persist for more than two to four weeks or continue to grow. Immediate medical attention is recommended if the nodes feel hard, fixed, or irregular, rather than soft and movable. Additional concerning symptoms include fever, night sweats, or unexplained weight loss. If the swollen lymph nodes are extremely tender or painful, or if the skin over them becomes red and warm, it could indicate an infection requiring treatment. Any swelling in unusual locations, such as above the collarbone, should also be evaluated by a healthcare provider.