Thank you very much for your response.
Hi. This is quite a tricky one to respond to. The blood values put her in stage 2 of kidney disease. That means a restricted protein diet (as in all prescription kd dog foods) is not necessary just yet. Once she moves into stage 3, then it becomes much more significant. However, any protein that is given should be the highest quality, and that means ideally human grade meats and poultry.
In the case of allergies, it is often productive to use unusual proteins. Something ideally your dog has not had before. So duck is a good one, so too is rabbit. Dry foods are invariably bad for all dogs (they contains lots and lots of preservatives and chemicals), but they are much worse for kidney dogs as they contain no water content at all (cans have about 80%) and the preservatives in kibble dramatically increases the toxins in the canine body.
You may never find out what started the allergies ... and once an allergy starts to become a problem, a dog seems to become even more sensitive to an ever-increasing list of things. It is indeed the immune system that's at fault here and there is no easy remedy.
I would stick to the old diet (canned) for now and see how things go. Supplement with pure coconut oil or pure organic salmon oil (with a vitamin E cap) or natural honey - in rotation - and just a teaspoon dose of each ingredient. You should also add a little amount of cooked chopped green cabbage, which will help offset any stomach ulcers forming. To help the kidneys, feed tiny amounts every 2 to 3 hours if that's practical. Smaller and more frequent amounts prevent the kidneys being stressed by having to deal with a large meal all at once.
Has your vet undertaken a blood pressure check? This is very important and needs doing if it hasn't already been done.
The only problem I have with Natural Balance is the fat content, which is a huge 44%. This may ultimately give rise to pancreatitis, if you aren't very careful with it. It's actually a reasonably good dog food, but that's one very big drawback. What you might do is try giving half the usual amount and then substitute the remainder with a few kidney friendly ingredients that you also know won't cause issues with the allergy. It may take a little trial and error to work it out, but I'm sure it would be worthwhile.
Tony