Adenitis, or swollen lymph nodes, primarily results from bacterial or viral infections. Common infectious causes include throat infections, measles, ear infections, gum and dental diseases (including abscesses), mononucleosis, and skin or wound infections. Less common infectious causes include HIV (the virus that causes AIDS), tuberculosis, sexually transmitted diseases like syphilis, and infections such as toxoplasmosis. Adenitis can also develop due to non-infectious causes, which include the use of certain medications, exposure to allergens, and, rarely, cancer. Swelling in the lymph nodes is generally an indicator that the body is fighting an infection or illness, and the lymph nodes usually return to their normal size once the underlying condition resolves.