Speaking as one who's been through what you're going though, in trying to find hypo-allergenic dog food, there are three types I use:
Dick van Patten: canned dog food (without chicken as it's a chicken allergy I'm testing for) If it is Beef food, it only has beef in it, no chicken.
Fromm: Duck and Potato or Lamb and Rice or Whitefish and Potato
Nutro Performatrin: Lamb and Rice Puppy formula
Duck and Whitefish are considered to be the staple of a hypo-allergenic diet more than Lamb, which is starting to gain popularity in many dog foods.
Karin listed some great foods, that I myself haven't tried. Rabbit and Venison are supposed to be great for allergic dogs. But it can be hard to find. I know, because I haven't found it here yet.
Allergies in dogs can cause recurring ear infections. At least that's what my Vet said. If you do get an allergy test done, which I haven't due to cost, you can expect to pay upwards of $500 or more. I don't know how much it is to test a human, but I'd think that it's a bit pricy for a test done to the blood. My opinion though, because it can be so worth it!
Let us know how it goes with your little guy!
"Always be a first-rate version of yourself, instead of a second-rate version of somebody else." - Judy Garland