What Causes Rashes All Over The Body?

I developed a total body rash (except the palms of my hands and soles of my feet), accompanied with palm sized ulcers on my lower left leg, severe dry skin that is very itchy. Have been using cortizone and gold bond ultimate healing lotion which has made my skin better, and a compression stocking and unno boot on the ulcerative leg. However, now something new has arised. I am amazingly thirsty, and drink 15 to 20 tall glasses of water each day, my taste of food has changed and my urine (infrequently - maybe three times a day) has become very dark. About the color between iced tea and coke.