I've been dealing with something similar all spring/summer and need to eventually go see the doc, but plain old benedryl (or generic that is incredibly cheap at Costco) helps me wonders. I get it on my feet, legs, and sometimes the top of my hands. I think allergens are super bad this year out where I live because it's been so hot and dry. I can tell you that I'm about the furthest thing from being happy when it happens to me though.

Hope you don't have to deal with it for long!