You can also view previously answered questions in the HSW Question Archive . When your body temperature rises because of an infection, it is called a fever . Fevers are caused by chemicals called pyrogens flowing in the blood stream.
Pyrogens make their way to the hypothalamus, which is in charge of regulating body temperature.
When pyrogens bind to certain receptors in the hypothalamus, body temperature rises. IL-1 is produced by white blood cells called macrophages when they come into contact with certain bacteria and viruses. IL-1 has multiple purposes, one of which is to signal other white blood cells called helper T cells into action. One purpose of a fever is thought to be to raise the body's temperature enough to kill off certain bacteria and viruses sensitive to temperature changes. Aspirin, for example, will reduce fever.