Cradle cap or something else?

[GreasyHairDoNotCare]

My 7 month old has had what I though was cradle cap for about 3 months now. Spoken with HV and been using cream ( E45, aveeno or sudocrem). It stared off as a small patch about the size of a 5p piece but now has spread. It also comes and goes, it will be nearly gone one day and then come back much worse the next. Could it be anything else. Pic attached

It looks like cradle cap - but it's quite red, could it be infected?

The only thing that worked for us was olive oil (but I think any veg/plant oil would work), leaving it for a few hours, then combing it out & washing well. We used a nitty gritty comb, but any fine comb would work I think.