Riley had problems with dairy when I was nursing him , ie if I ate too much, then he would get fussy, gassy, sniffly nose etc. When we tried cows milk at a year, he had really mucosy diapers, his excema came back, he was very cranky. So now he is on rice milk, and can handle yoghurt okay. Cheese he can eat a bit of it it is cooked in dishes. He doesn't like it all that much anyway. He reacts pretty much right away.
I think most peds recommend holding off on yoghurt etc until well gone the nine month mark at the earliest, maybe your lo just reacted then because he was too young, not because of a real allergy/intollerance.