My 90 Yr Old Father Is Taking Spironolactone 25mg And

My 90 yr old father is taking Spironolactone 25mg and Furosemide 20mg for edema. He has had a rash all over his body that iches him and he is very uncomfortable. The dermatologist has suggested prednisone 40mg pack to 10mg to stop the itchy and rash. I am wondering if it is the medicine furosemide. Is there any other diuretic to take instead of this one?