Lymph nodes are small, bean-shaped structures distributed throughout the body, including the neck, armpits, and groin. They form a crucial part of the lymphatic system, a network of vessels and organs that support the body’s immune defenses. These nodes function as filters, trapping harmful substances such as viruses, bacteria, and damaged cells from the lymph fluid before it returns to the bloodstream. When lymph nodes become swollen, a condition known as lymphadenopathy, it typically indicates that the immune system is actively working to combat an infection or illness.
Causes of Lymph Node Swelling
Lymph nodes enlarge when the immune system responds to an infection or inflammation. When the body encounters a pathogen, immune cells within the nodes multiply and gather to fight invaders. This increased activity causes the nodes to swell. The location of the swollen nodes can often provide a clue about the source of the problem, for example, a throat infection might lead to swollen lymph nodes in the neck.
Common viral infections are a frequent cause of lymph node swelling, including the common cold, flu, and mononucleosis. Bacterial infections like strep throat, ear infections, or skin infections can also trigger this immune response. Less commonly, swollen lymph nodes can result from autoimmune conditions, where the immune system mistakenly attacks healthy tissues, or in rare instances, certain cancers like lymphoma or leukemia.
Typical Duration of Swelling
The length of time swollen lymph nodes remain enlarged depends significantly on the underlying cause. For common viral infections like a cold or the flu, the swelling typically subsides as the infection resolves, which can take a few days to a week. However, the nodes may take several weeks to return to their normal size, even after other symptoms disappear.
In cases of mononucleosis, swollen lymph nodes can persist for a longer period. While many symptoms of mono resolve within two to four weeks, the enlarged lymph nodes might remain swollen for several weeks or even a few months. For bacterial infections, the swelling usually reduces once appropriate treatment, such as antibiotics, has cleared the infection. Lymph nodes can sometimes remain slightly enlarged or firm for an extended period, even indefinitely, after an infection has completely cleared.
When to Seek Medical Attention
While swollen lymph nodes are frequently a sign of a routine infection, certain characteristics warrant medical evaluation. Consult a healthcare provider if the swollen nodes appear without an obvious reason or do not decrease in size after two to four weeks. Nodes that continue to grow, feel very hard or rubbery, or are fixed in place (not moving when pressed) should also be checked.
Other concerning symptoms accompanying swollen lymph nodes include unexplained weight loss, persistent fever, or night sweats. Swelling in lymph nodes located near the collarbone or in the lower part of the neck also merits prompt medical attention. If the skin over the swollen node becomes red or inflamed, or if there is difficulty breathing or swallowing, seek immediate medical attention.