Difference between 'normal' baby acne and eczema?

[BarrelOfMonkeys]

DD is nearly 7 weeks and has had spots since end of week 4 all across her cheeks. GP advised E45 cream, as 'we don't want it turning into eczema'. My question is, how do I tell if it is eczema or not? Neither DH or I have sensitive skin or skin problems so it's a new area for us. It's spread up her forehead and is creeping round her neck, but doesn't seem to be bothering her. (She's been on formula supplements since day 10 so not sure whether it could be a dairy allergy - would it have flared up earlier if so?)

My DS had this too but the HV said it was normal milk rash
He is BF..so don't know about FF babies though re dairy allergy..
Used E45 cream and found it got worse, DS's has almost cleared up now at nearly 6 weeks and he had it since 1 week old, spread up onto his head and down his neck and chest but all seems to be clearing up, hope your DD is the same