Why Do Lymph Nodes Swell?
The lymphatic system works like a highway of one-way lanes, pushing lymphatic fluid full of immune cells throughout your body. Along the way, the fluid passes through about 600 bean-shaped nodes located in clusters from your knees to behind your ears. When immune cells detect "bad guys" like viruses or bacteria, they trigger the nodes to boost their disease-fighting cells, causing swelling to fight off the infection.
What Do Swollen Lymph Nodes Feel Like?
Normally, lymph nodes aren't visible. But when swollen, you may see or feel rubbery nodules the size of a pea, cherry, or even a plum—either soft and tender or firm.
Common Causes of Swollen Lymph Nodes
- After vaccination: Vaccines need to spark an immune response to be effective. Cells in the lymph nodes expand to produce antibodies, causing swelling that typically subsides within about a week.
- Common infections: Upper respiratory infections, strep throat, ear infections, infected teeth, measles, mononucleosis, skin infections, tonsillitis, and pink eye can all cause swollen lymph nodes.
- Less common infections: Tuberculosis, toxoplasmosis, and certain STIs (like HIV or syphilis) can also cause swollen lymph nodes. If nodes are swollen in two or more areas of the body, it may indicate a wider systemic problem.
- Autoimmune disorders: Certain autoimmune diseases can also cause lymph node swelling and require medical diagnosis.
When Should You Call Your Doctor?
Most viral infections will fade without specific treatment, but if symptoms become increasingly uncomfortable, it's best to reach out to your doctor. Bacterial infections—like strep throat or some cases of pink eye—require antibiotics. If swollen lymph nodes persist, keep growing, feel hard, or are accompanied by unexplained fever, night sweats, or weight loss, seek medical attention promptly.
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