I have extreme seborhic dermatitis on both my scalp and eye lids. I went to a naturopathic chiropracter who practes applied kinesology and cold laser therapy. The best dermatologist and doctors in the Salt Lake Valley kept prescribing sterorids, and medicine and nothing worked. I finally went to a doctor who did cold laser therapy on my eye and scalp three times a week for six weeks and it is completly gone, and hasn't come back as of yet, and it has been over six months, I call him my miracle doctor. If you want more info on this type of doctor they use all natual cures, no prescriptions etc. check them out online.
i don't know about diaper rash... but I would ask Dr about having a steroid in the medication in any case. In fact, the reason I looked up this particular combination of drugs is that my doctor gave me the combo Nystatin instead of plain Nystatin. I am now calling her office to complain and ask for a new script for plain Nystatin because it was done without consulting me when I asked for prescription renewal. I use Nystatin by itself -- no additive/added drug to control yeast infection which comes from the rectum when I have eaten foods that upset the balance of "good organisms/bad organisms". If your digestive tract is unbalanced (a lot of flatuance is a clue), that alone can contribute to vaginal yeast infection -- or possibly diaper rash (I have no experience with a baby needing more than cornstarch or "butt paste" to control diaper rash -- which works fine on the worst case my grandson had).