Fever is defensive climate change pushing an invader outside its ideal temperature. Most animals increase their core temperature when they are sick. Fish swim into warm waters, lizards bathe in the sun. Bees heat up the air inside their hive.
Pyrogen, “The creators of heat” float and pass right into your brain, where specialized receptors pick them up and crank up your internal thermostat. First you begin to shiver. Your skeletal muscles contract really quickly, which generates a lot of heat in your core. You burn about 10% more calories to stay alive for every degree centigrade you rises. The elevated temperature is harmful not only to antigens but also to the body's own cells. However, it is optimized for the immune system.
If you are sick, you are supposed to feel a reasonable amount of pain so you lie down and save energy. Fever is not a bug but a feature of your immune system. But pain and fever are closely connected and over the counter Painkiller also work against fever. In general it’s fair to say that for temperatures below 40, fever is not dangerous and does not to be treated except pregnant woman, seniors, and seriously weakened patients. Fever over 40 is dangerous to anybody because it is most likely cause by your internal heat monitor fail. There are also evidence that for some diseases like influenza and chickenpox antifever drugs do not help you to heal faster. Also, there are strong indications that more people may survive serious infectious diseases better with a fever. In summary, you decide to feel bad without drugs, you can rest easy in the knowledge that your enemies are having a much worse time than you.