I am having a stinging/prickly sensation in my skin with tiny bumps (almost like sandpaper) whenever I workout?

I had chemotherapy 5 months ago and now, whenever my body heat rises from working out, or being in hot weather, or having a hot flash, I get a prickly rash and stinging sensation on my skin. It resolves when I stop working out, or bring down my body heat with a cold towel or fan. Has anyone ever heard of this reaction from chemo - even so long after having chemo? What is it and how to keep it from happening?