Lymph nodes are small, oval structures found clustered in the neck, armpits, groin, and throughout the body. The lymph system responds to infections and foreign substances. There are several components consisting of lymph glands (nodes) and small vessels that link all the nodes and the spleen. Infection-fighting white blood cells also travel to the lymph nodes where they trap, attack, and destroy the foreign particles. Localized infections are confined to glands swelling in a limited area such as only in the neck with a throat infection.

Lymph nodes enlarge when they fight harmful germs or as a reaction to other foreign material. The range of symptoms includes:
* One or more swollen lumps.
* Possible tenderness when touched.
* May feel hard and not moveable.

Swollen glands can cause pain and tenderness during colds, flu, sore throat, strep throat, or ear infections. Lymph nodes can also swell with diseases such as mononucleosis, Hodgkin's disease, cancer and HIV. Other reasons for swelling include:
* Side effects from some seizure and thyroid drugs, sulfa drugs, iodine, and penicillin.
* A collection of lymph fluid due to blockage (lymphedema) that may be caused by surgery, radiation treatment or cancers.
* A tumor of the lymph gland.

Enlarged, painful lymph glands are usually common reactions to infection. Seek medical evaluation for:
* Multiple swollen nodes not associated with a specific site of infection.
* A painless lump that feels hard.
* Enlarged lymph glands that do not go back to normal within a few days.

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