I fed one of mine the hydrolyzed diet for about 6 months while I figured out what he was allergic to. I did not view it as a lifetime commitment! This was over 10 years ago but I seem to recall he did improve slowly. In his case he was rawfed before the allergies and, as luck would have it, we discovered (through an elimination diet) his allergy was to chicken and to beef. So he got put on a fish based kibble, end of problem.
By the time I went the Z/D route, we were at mucousy stools, constant ear infections, hot spots etc.
To the other questions, it has been enough years most of the answers have fallen out of my head.
When another one developed a flea allergy and pyoderma from it and the regular expensive veterinary antihistamine did not work I used benedryl at the dog dose (which is every 8 hours...much higher than human dose) and gave her oatmeal baths. Fleas gone, issue gone.
NAPWDA Certified Cadaver Dog
Waiting at the Bridge (italics
=GSDs) (hemangiosarcoma=blue):Grim , Cyra, Toby
, Rainbow, Linus, Oscar
, Arlo & Waggles