Body & HealthHow it works
Why you feel cold when you have a fever.
During an infection, immune cells release messenger molecules called pyrogens. In the hypothalamus they trigger prostaglandin E2, which raises the body's temperature set point from about 37 to, say, 39 degrees. Your body now reads itself as too cold, shivers and narrows skin vessels until the new target is reached. When the set point drops again, you sweat.
Useful: So chills mean the temperature is rising right now; sweating means it is falling.
Source: en.wikipedia.org