What Causes Inflammatory Skin Rash Associated With Celiac Disease?

It appears that I have DH, the inflammatory skin rash associated with celiac disease, even though I had blood work done for celiac, and it came back negative. Nothing helps the rash. I apply Desitin when it flares up extremely, but any other cream/lotion irritates it. Some days I itch it until it bleeds unintentionally. I was wondering if tanning in a tanning bed would help make the rash go away, because I have been completely gluten free for almost a month now, and it has shown no signs of letting up.