It sounds very similar to the rash I had earlier this year. It took about 3 months to go away and pretty much one solid month of using steroid cream. The steroid cream was not fun as one's skin gets very addicted to it, and when I stopped using it, my skin got worse for about 10 days before it got better.
What I had was contact dermatitis. I'd had it only in a few patches for a very long time, then when I got a skin infection all through my system, the dermatis went almost 100% all over. I still get the dermatitis once in a while, but it's very isolated and has remained isolated for four months now.
We never found out what caused it, but we think stress, both physical and emotional were huge contributors. I know if I feel a little sick, or am overwhelmed by something, the isolated patches that still have the dermatitis flare up right away and take about a week to calm back down. Fortunately, I don't need to use the steroid cream anymore, but an Aveeno oatmeal bath always is a good idea to sooth any itching due to the dermatitis.
My derm instructed me to make sure I never wore clothes more than once before washing them, change bath towels and washcloths daily, and change the sheets 2-3 times a week, more often if I could manage it. She also had us go through the house and get rid of almost all cleaning products except for bleach and vinegar, and to use only liquid dishwashing soap as a detergent for my laundry/sheets/towels. Her reasoning was that she wanted to reduce every possible skin irritatant I was coming in contact with. While it didn't seem to reduce the dermatitis in any way that we could immediately tell, we did notice that after my skin recovered, keeping up with her instructions has made my skin look and feel a lot better. I'm much paler now (I used to look soooo red) and have a lot less peeling.
Oh, the doc also put me on doxepin, which was originally manufactured as an anti-depressant. However, a big side-effect is that it relieved itching, and made me really sleeping, so if I was having a hard time sleeping because my skin was hurting, or it was daytime and I was hurting so bad I couldn't do anything, she'd have me take one doxepin with the option of taking one every four hours. I found that just taking one in the evening, and then one at bedtime helped a lot, and I was then able to function during most of the day time with less discomfort. Making sure I get a full night's rest has always been important for my skin, but it became a top priority while I had the rash. If I didn't sleep very well, the rash got much worse.
I am female, and was born in 1972 with Lamellar Ichthyosis.