I've Been Having Intermittent Flushing Of My Hands And Feet.

I've been having intermittent flushing of my hands and feet. (red, tingling, pulsating). Originally itwas accompanied by spikes in BP and heart rate. If I get in a shower and raise my entire body temp the redness goes away. Have it some days and not others.....followed by extreme cold. All blood tests come back okay, as does 24 hour urine test. ???????? 74 years old. Take sythyroid, and Toporl XL.