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During the first period of fever (体温上升期), because the set point in turned up a few notches, your normal body temperature is regarded as a cold stimulus, and the temperature regulating center reacts to cold by making sure that heat generation > heat elimination. It sends commands to the “heat eliminating department” (the skin) to constrict peripheral blood vessels of skin, reduced skin blood flow causes palor. There is also action by the “heat generating department” (the muscles) via寒战, which causes musculo-skeletal metabolism to increase up to 5x.  Also, renal blood flow decreases, causing urine volume to drop significantly. 

During the second period of fever (高热持续期 or 热稽留期), the body heat has already risen to the new set point. Here, heat generation is as much as heat elimination, but maintained at a higher temperature. 寒战 stops as it’s hot enough. Your peripheral vessesl on the skin start to dilate cause it’s hot. Skin color is red. Heat inside due to pyrogenic factors causes sweating (compared the following period when it’s the absence of pyrogenic factors and the subsequent reduction in set point that causes sweating) as well as dispersion of fluids from airways. All this causes dehydration of skin and mouth.

During the last period of fever (体温下降期), you start to be able to urinate again. When the pyrogenic factors are eliminated, the set point is reduced to normal again, and the hypothalamus says to reduce temperature, causing peripheral vessels on the skin to dilate, and here we have sweating, all in all the sweating reduces temperature very rapidly. Note that it’s not sweating that cures the disease, but more likely the following:

1. elimination of toxins via immune system allows the体温下降期 to come into play.
2. sweating may be induced by herbs which takes away the heat, but maybe not the pyrogens.