You may need to get a second opinion from another doctor. Lymph nodes are glands that play an important part in your body's defense against infection. They produce lymph, which travels throughout your body in the lymph system, and filters impurities in your body. Usually occur in the groin, armpit, neck, under jaw/chin, behind ears, back of head. Infection, inflammatory conditions and abscess or cancer can cause swollen lymph nodes. Most common cause is due to infection. When lymph nodes increase in size suddenly and painful, it is usually caused by injury or an infection. Enlargement that comes on gradually and without pain may result from cancer or a tumor. Some of the causes of swollen lymph nodes include mononucleosis, German measles, tuberculosis, mumps, ear infection, tonsillitis, abscessed or impacted tooth, gingivitis (swelling of the gums), mouth sores, and sexually transmitted diseases. Immune or autoimmune disorders that can cause swollen lymph nodes include rheumatoid arthritis and HIV. Cancers that can cause swollen glands include leukemia, Hodgkin's disease, or non-Hodgkin's lymphoma. Which lymph nodes are swollen depends on the type of problem and the body parts involved. Identifying the location can help determine the possible cause. Swollen lymph nodes may also be caused by some medications, like phenytoin for seizures, or certain vaccinations such as typhoid.