It's good to be back, Twig. I wax and wane in my attendance somewhat fierce...
Yes, Blue Buffalo is available at the two major pet supplier chains in the area, PetCo and PetSmart (though PetSmart has a better variety, including the brand's biscuits, which my boys love), and is available through at least PetSmart's website.
Allergies are really a very common thing in pet dogs and cats, moreso than most people imagine. A lot of common symptoms that people chalk up to fleas or "sensitive skin" or a "sensitive tummy" tend to actually be allergies that can be mostly corrected by a diet change. (you may still have a Delicate Flower of a puppy who has a sensitive tummy though, but the food change will help)
Chicken and corn are the two things dogs tend to be the most sensitive to, followed by beef, wheat and soy. The best way to avoid the allergens is just like what you do in people; you either go all out, by beginning a completely allergen-free diet, typically hand-made (and a pain in the butt, may I add), or just pick a single-source protein/grain food and see how that goes. If it doesn't work, try another. Such as, starting with lamb and rice, then trying venison, then fish, or whatever. It's hard to get away from rice, if your dog is sensitive to all grains, but low-grain and grainless formulas do exist, typically advertised as "high protein" or "wilderness" type diets (such as Blue Buffalo Wilderness, or Innova EVO).
Also, though i think your two brands to measure up to this, make sure you are feeding a food with no by-products, and no corn. By products are all the extra ickies that don't count as "meat." And, despite what some companies say ("we use only chicken, never chicken meal!"), the -meal ending is actually the "chicken" that has been dried-- therefore, the water count is much less, and if the ingredient "chicken meal" is #1 on one food and "chicken" on another, the one with the "meal" has more chicken in it because the water has been removed! The semantics of dog food labeling are interesting, to say the least.
Kestrel ~ Kayla