Lymph nodes are normal part of the body structures that hep produce and at times store some of the white blood cells (lymphocytes) and antibodies that help the body fight against infections and foreign bodies it is exposed to. When there is infection in the body, they work harder to produce more of these foot soldiers so they may increase in size, feel hot and/or painful to touch.....As soon as the infection is treated, they go back to normal size. They can also increase in some cases of cancers