About 10 years ago, I had a dog with very bad allergies and when I was doing research then, I ended up switching all of my dogs to raw feeding. It made a tremendous difference for my boy, and since then all of my dogs have done well on it. I had another dog that still got seasonal allergies ( licked the same spot on her paw every year, and I could almost call it to the day, when it would start) but other than the hot spot, no allergies.
It has worked well for us in minimizing the issue.

Agree with raw feeding, that's what cured my dog. If you don't want to do raw, at least feed grain free. Nature's Recipe is a good one that's not quite as expensive as the others. You can get a great deal on Chewy (google chewy free shipping) if you set up regular deliveries. You might have to add one small other item in order to qualify for the free shipping minimum.

Good luck ~

What food is your dog on now? Try a food that's very much different than what you are currently feeding. My dog has an allergy to the peas that they are putting in almost all of the grain free recipes. She's on Natural Balance LID food right now trying to narrow down her allergies which is how we figured out the peas. The new food has no peas but all the other foods she was on had just peas as a common ingredient, nothing else. We actually just got lucky figuring it out! Had there been multiple similar ingredients, we would not have known.

I'd start by eliminating the corn, wheat and soy and see how that goes. Perhaps try a lamb and rice food and see how that goes. It's very hard to say because every dog is just so different.