Hives,eczema,baby acne or heat rash? It's around his face,ears,head,neck,top of back,arms and a little on legs. It…

Hives,eczema,baby acne or heat rash? It's around his face,ears,head,neck,top of back,arms and a little on legs. It started off as a couple red bumps on face and doctor said it was heat rash but now these little bumps are everywhere except his stomach,chest,lower legs and lower back. I'm not sure on how to treat it. I know when I tried coconut oil once for his cradle crap in eye brows he had like an inflamed reaction so I think he may be allergic to that.