This is because when a person becomes sick its means that the bacteria or virus that had entered in the body of the individual has predominated the immune system and the lymphocytes which are present in the lymph nodes have lost the fight. Therefore the bacteria which is transported into lymph nodes to be destroyed if dominated starts proliferation in those lymph nodes and they become swollen or painful.
This is because when a person is sick its means that the bacteria is predominated into the individual’s body and the lymphocytes which were fighting against the bacteria have lost the fight. Therefore the bacteria which was transported by the macrophages or the neutrophils into the lymphatic vessels and then through the lymphatic vessels they enter the lymph nodes and after defeating the immune system i.e the lymphocytes there it starts proliferation and therefore the lymph node becomes swallon or painful.
This is because the system have and energy debt and unable to supply energy for the nodes
