I most likely have DH. I go the the derm next month, and hopefully they will do a biopsy at that time since it takes 3 months to get in there! But after reading another post on here, I put some iodine on a bandaid and put it on my arm. It was itchy almost immediatly, but I left it on for almost 24 hrs. I took it off 2 days ago, and I can still see exactly where the iodine was. It is all red and bumpy, and the rash is shaped like a perfect rectangle from the pad on the bandaid!