Suggest Remedy For Itchy Rashes On Back

I have an irritating rash on my back and bottoms which has been there since 2003 initially i had an std syphilis to be precise but now its not there but the rash is still there and it is really irritating especially when its cold I have seeked medical advise but all the doctors say is its a mild allergy furthermore the skin around my skin is constantly peeling off please advise me on the problem i could be having.