Update 6 months later:
I had him on Orijen Adult since June and he was doing superb!
I went to the pet shop to get him another bag and they convinced me the Orijen Senior would be better for him since he is going 11 in a few months, they said after 8 years young they should be started on senior.
2-3 days later, he is eating it, but seems just a bit sluggish than usual. Should I keep him on the Senior guys?
Thanks!
PS> He loved the adult food, was eating a few cups a day and he actually looked healthier than the last few years! I'm so thankful for having switched from Procter & Gamble's Wellness core, which may have been the reason for this allergies too.