Any of the above could be the one TRIGGER to his itching, OR SEVERAL can be the trigger to his itching.
1st I would stop all of the 'foo foo juice' (the 'smell like something other than a smelly ole dog perfume')
Eliminate EVERYTHING and start at the basics -
1) His food, was low Grade, and you switched to a high grade food (YEA ! ! ! !) however... what was the PROTEIN source in the original food? - one possibility on the list - he might be allergic to the new protein source.... are you Slowly doing the switch? Mixing old and new food?
2) once you eliminate all the perfumes - look for shampoo for allergies
, or sensitive skin.
3) the 'Deodorizer' for the marking, it should be an Enzyme cleaner - we use natures miracle - follow the directions closely
4) he's new to the house. it could be something like your Fabric softener or Laundry Detergent he is allergic too. This is a brand new environment to him.
5) yard - is he your only dog? have you used any lawn chemicals, fertilizers this year?
I think you are getting the idea, that it could be ALL or just one of those things, start out simple, it will be the ONLY way to tell. Blue Buffalo also sells a 'Blue Basic' which is limited ingredient (we use it for Gizmo and Hershey)