What Is Fever?

Fever is higher-than-normal body temperature (over 37.5ºC) and occurs in response to an infection or inflammation. It’s triggered when your body’s immune system responds to pyrogens (fever-producing substances) such as viruses, bacteria, fungi or other toxins. Pyrogens ‘tell’ the hypothalamus to increase your temperature set point. As a result, you skin feels hot and looks flushed/red; you have bodily aches and pains and you may sweat, shiver or feel cold.