Hello. I was wondering exactly what causes a fever. I ve read and seen how they say that actually it is not caused by the cold, only bacteria and other pathogens, and that the cold simply increases your chances of getting a fever because of how your blood vessels constrict and your immune system weakens in the winter. However, I have heard from someone that you re body has lots of dead cells and membranes with viruses in them (Or something like that), and that they are inactive, but when you go outside, in the cold, you are more likely to get a fever, as those viruses (Again, or whatever it is) become more active. An idea just popped in my mind. The idea is what if those viruses don t become more active, but your immune system just gets weaker, combining the first and second ideas. I currently hope in the first idea, though. The person told me that the first thing is what orthodox doctors and facts say, but the second thing is what it really is. Please let me know whatever it is that REALLY causes a fever.