how much should a puppy scratch ?

I have a question about scratching, I know that some scratching is normal but how much is not normal. Rusty seems to be scratching a good bit all over. Mainly on his mouth and on his side near his rear legs. Could this be a food/allergic reaction ? Im feeding him Innova Evo and he loves it. I would have to swap foods and find out that had nothing to do with it. Any suggestions?

Maybe a trip to the vets is in order
It could be Fleas or a Skin Allergy.

went to the vet yesterday

Believe it or not we went yesterday and they told me had had no fleas and there were no signs of any allergies.. he has one spot on his side that i think irritated him for a while and they said to just watch it and see if it gets better, but they said his skin was fine.. I was just wondering because i think he is scratching too much could just be my imagination lol