Extreme itchiness when right before sweating or heart rate increase

[drob31]

There are times, and it seems random, where I get extreme itchiness mostly in my legs, but can sometimes be on my hands. It seems to be right before I get to the point of possibly perspiring in these areas. I scratch and scratch and there are no hives, nothing is there, but the scratching helps a little and eventually it goes away.

At one point I thought caffeine caused it, but it can occur without caffeine.

 

[ScottTriGuy]

Ditto, except I only experience it on my forehead.