Suggest Treatment For Rashes All Over The Body

Hi. I am a 26 year old female who has never had a rash or allergies. In August I started working out regularly and developed a rash. The rash has been all over my body at time. It only itches on my feet, hands and finders. The look of the rash seems to change. At times it looks like hives and at times its a small red dot with a white halo. I ve been to the doctors several times. I ve seen a allergist twice. When I am prescribed a antihistamine, it seems to make the rash worse. Also at night the rash goes away, but once I wake on the morning it starts back up. Like I said it started when I was working out and sweating daily but I stopped working out for a week and the rash was still there. I ve had blood tests done and everything was fine. I haven t gotten sick as in throwing up so I feel a food allergy is thrown out. I ve felt more tired lately and sometimes my breathing is difficult. Any ideas?