confused about milk intolerance

ok, so we have kept Jason off all dairy, even in baked goods for just about a year now. We went to my inlaws house for dinner the other night and they had cheddar cheese out on the table to snack on. Of course Jason climbed right up and grabbed a piece before I could stop him. I scooped most of it out of his mouth, but I’m sure he swallowed some. I was expecting the usual… horrible mucousy diarrhea, inconsolable crying, and a really bad diaper rash…but nothing happened!!! Just last month though, he got a hold of one sour cream and onion potato chip and it was horrible for 2 days!!! It’s like acid in his diaper he screams so much!!! So, do I take a chance of putting him throught that again and trial some dairy??? Is there something different about cheddar cheese that wouldnt cause the same symptoms? or did we just get lucky?? Any thoughts??