Extreme Rashes

My daughter developed a rash all over her body in Aug.08 at the beach and was taken to the ER. She had puffy swollen eyes and itching, burning. They gave her prednisone and a shot of epi. which cleared it up. Then a week later it reappeared and same thing back to ER. From there we went to a dermatologist to an allergist and she was tested for everything not allergic to any but it's something with her autoimmune system that is causing this and she had been on the prednisone for 6 months straight then that quit working so we were referred to a specialist in Charleston, SC and she was put on around 6 antihistamines and 10 benadryls a day but had to be put on homebound from school because she couldnt function with all the pills, but it did clear up. Now it keeps coming back and they try a prednisone pack which works good for about a week or 2 then reappears again. So i dont know what else to do or who else to go to, if you have any advice or suggestions PLEASE fill me in. We are really struggling with this and it really affects her schooling. Thanks Alot!!!!