A lymph node, a part of the body that recognizes infections, is enlarged or swollen if it is more than 1 centimeter wide, according to MedlinePlus. Swollen lymph nodes can have many causes and subsequent treatments but usually stop being sore within a few days.
Swollen lymph nodes can be felt in various places such as the groin, armpit, neck, behind the ears and on the back of the head, states MedlinePlus. The location of the swollen lymph nodes is dependent on the cause. Several causes of swollen lymph nodes include infections, immune disorders, cancers and medications. Painful nodes that swell suddenly are usually due to infection, and those that appear slowly and painlessly may be due to cancer. Seizure medicines such as phenytoin and typhoid immunization can also cause lymph nodes to swell.
Swollen lymph nodes may take a few weeks to return to their normal size after fighting an infection, according to MedlinePlus. More serious conditions occur if the lymph nodes do not get smaller after several weeks or if they continue to get larger. Any node that is larger than 1 centimeter in diameter is a cause for concern. If lymph nodes are red and tender or feel hard and fixed in place, then there may be a more serious underlying problem. If a serious cause is detected, treatment can include medication and hospitalization.