Pyrexia. People really do not link pyrexia and cold, still, it is connected. And naturally, people often do not collegiate pyrexia to sinus infection also, which is not correct. Still, this is an infection, though it comes from simple cold for instance. Pyrexia causes inflammation, and the patient’s immune system uses all the opportunities and reserves to ensure soon recover of the organism. When this occurs, and the body of the patient becomes occupied close to dangerous bacteria, viruses and so on, the body naturally raises its temperature to help to resist uninvited invaders.