According to the facts of physics, if temperature increases, thermal expansion of an object is positive it will expand and with decrease of temperature it will shrink. Pressure will increase due to increase of temperature.
On the contrary, during fever we can see blood vessels and skin are shrunk, pressure decreases, body shivers, sleep increases, motion decreases, inflammation increases, body pain increases, blood circulation decreases, dislike cold substances etc...
In fever, the firing rate of Warm sensitive neurons decreases, and the firing rate of
Cold sensitive neurons increases.
At the same time if we apply hotness from outside by thermal bag or if we drink hot water, our body acts according to the Facts of Physics- increase of temperature pressure will also increase, expands blood vessels and skin, body sweats, motion will increase , inflammation will decrease , body pain will decrease, blood circulation will increase, like cold substances etc..