What Causes Itchiness In The Body Whenever Temperature Raises?

Hello
I get extreme itch whenever the temperature of my body rises (or so I think). Earlier it used to be my hands only...I used to get a very irritated feeling. The it started with my hands and feet both, and now my whole body. Things like brisk walking, or even slipping under a duvet cause this. I'm really worried as to what It can be. I'm 25 YO Male, Asian and have had no medical complications (except shingles two years ago)

Please help.