What Causes Rash On Elbows, Arms And Lower Legs?

Yes thanks. I have a cluster rash that started on my elbows and became three dimensional. Then as that started to subside I had more rashes on my arms, the back of my lower legs, and on my hips. This second set of rashes was less dimensional and more like red clusters. They itch and do not seem to go away with salt baths and benedryl. I do not have any other symptoms except an occasional stomach ache. But I have had stomach issues for quite sometime. What is this?