Yes, you need a presription. I think it might be better to ask a primary care doctor instead of a dermatologist. The dermatologist will want to examine your dry skin unlike a primary care doctor. A dermatologist might just give you a small sample size instead of a prescription and make you come back to examine your dry skin for prescription in a couple weeks.
I got my sample for free from a dermatologist, but you need a prescription. They pronounce it Epi-cream although it is spelled differently.