Rash just will not go away :(

Ok so I have a very bad case of athlete's foot. Doc prescribes griseofulvin, which works but three days into it i have a rash all over my body. I assume its an allergic reaction and discontinue use. Go see the doc and he thinks allergic reaction too, rash is everywhere. So he prescribes prednisone, 60mg for 5 days then 40 for 5 days and then 20 for 5 days. It brings the rash down to almost nothing, but after the 15 days are over it starts coming back. Then he gives me a topical steroid cream which works for the areas that I apply it but I run out quick and it comes back.
Next time the doc prescribes xantac and prednisone, but a very small dose of prednisone.. 20 mg a day for 5 days. I guess hes thinking the xantac might help clear out anything in my stomach causing the allergic reaction? Well the five days was over 2 days ago and its coming back slowly..
Anyone have any suggestions? Could it have anything to do with the bad case of athletes foot I;ve had it for about 7 months now.. the griseofulvin almost got rid of it, but when I stopped using it early it didn't kill it all and now its grown back to its original size.
Anyone ever hear of anything like this?