What is the difference between a fever, a hot flash, and a night sweat?

Fever is illness. Fever typically means that your body is fighting an infection and is "heating up" to help your normal cells in the process. A night sweat is just a nocturnal occurrence of a a hot flush. This happens in women starting to undergo the menopausal transition. As estrogen levels fall/fluctuate with declining ovarian function, the brain centers that control body temperature go a bit haywire...