Hives and Heat-Rash are common with Fibro, but you should search online for the precise kind of rash (WebMD & The Mayo Clinic are good sources) - it's important to narrow it down because they all get treated differently.
It took me a while to determine that while I had suffered from Rosacea for a time, what I now had was Psoriasis (and then later Nail Psoriasis, as well). I treat it all with Tar Shampoo and exposure to air. I have also been trying out fresh Aloe for between my toes when they get too inflamed and itchy. Steam and Sauna also help.
Like many Fibro sufferers I also get a Mystery Rash - mine is on my outside forearm just below my elbow (and only on the Left one). Weird, but that's Fibro for ya. That one I treat with an unscented Aloe Vera handcream.
Be VERY careful of using Steroid creams as they can lead to problems like infections, particularly for those like us with delicate (if not compromised) Immune Systems.

Thanks!!

What cream did you get? Did it work at all?