Adenitis, or swollen lymph nodes, is typically caused by bacterial or viral infections. Common causes include throat infections, measles, ear infections, gum and tooth diseases (such as abscesses), mononucleosis, and skin or wound infections. Less common causes may include HIV, tuberculosis, sexually transmitted infections like syphilis, and conditions such as toxoplasmosis. In rare instances, adenitis can also be a symptom of a more serious condition, such as cancer. Swelling of the lymph nodes is generally an indication that the body is fighting an infection or illness, and the nodes typically return to their normal size once the underlying condition is resolved. Certain medications or exposure to allergens can also cause lymph node enlargement.