What Causes Persistent Red Itchy Rash On Body?

I have had a persistent red itchy rash since Nov. that gets worse then better with no rhyme or reason, ie food, medications, etc. Some of the rash is red itchy bumps, some is red ovals and travels over all my body. Only place I haven t had it is on my face. Even had it on soles of feed, palms, and scalp. I had lyme disease a few years ago. Could this be a symptom of this or something else? It s driving me crazy...