I have had an itchy rash for almost a year. It started on my legs. Then as time went on it went to my knees and forearms and to the backs of my hands. Dermatologist put me on steroids and now that I'm off it's coming back. Also on lower flanks and fell itching in thighs. If I have a celiac test, will it show if I only have the skin reaction to gluten, or...