I have an itch, sometimes accompanied with a red rash that can swell. It mostly happens on my hands and lower arms. It also happens often on my feet, but rarely anywhere else. It is irregular in shape and varies in size, but usually does not cover the hand. I can happen in either hand or both.
I do not know if this is fibro related or not, so I thought I would see if anyone else has this. it gets so bad, that I scratch until I bleed. The itch and rash goes away as suddenly as it came, but I am sometimes left with reminders of it in the form of self-inflicted scratched.
I thought it must be allergy related for a long time, but I do not see how now because I have had it for such a long time and I have been paying attention to various substances I use and I am around and nothing external seems to be causing this.
Another possibility could be psoriasis. It can appear in several different forms, so it's worth your time to look at each type to see if it's what you have or not. (If it is, then you'd need a different course of treatment:)
Other causes could be eczema or allergies. I'm sure there are other things too, maybe even fibro? I'm not really sure but I'm sure that someone on here has the answer and will tell you.