The only thing allergy testing is going to do is help you to know what to keep Bella away from. We had Spooky tested and man she was allergic to everything. I'm pretty sure there were some things not on the testing list too, that I put in my own list of things. Spooky was allergic to grass, trees, different weeds and flowers, dust mites, mold, fleas, + +...... She also had food allergies.
It took us years to come up with the most natural way of helping her. Spooky had dermatitis so she would get little zit looking bumps that always got infected along with hives, hot spots, and lose a lot of her hair. Not to mention she would smell really bad and have the worst dry skin. If she got really, really bad we would give her Vanectyl-P which is a antihistamine and prednisolone combo. We tried not to give her the medication unless she needed it. For the average flare up we would try to boost her immune system (I make my own supplement), keep her away from certain things, put booties on her, and bath her twice a week with Nizoral. When you know what the allergies are (which you can usually figure out yourself by following patters and keeping a journal) you can do certain things to help. Like for Spooky we let her outside before the grass was cut and tried to keep her in (with doors and windows closed) for a few hours after. When we did let her out we were very carefull to make sure she didn't eat grass or other weeds, and I would bring blankets outside for her to lay on or get her to play on the patio or deck. We didn't let her in the basement certain times of the year, I never used dryer sheets for their blankets or stuff, tried to vaccum a lot (and vaccum an wash their bedding), I make a natural flea repellent and we tried to keep her away from dogs who we weren't sure didn't have fleas (all it took was one bite), etc......
Some people find that a raw diet helps a great deal. Although it doesn't help all dogs. We didn't keep Spooky on a raw diet because she could only have very expensive meat sources. At the time I wasn't a savvy meat shopper and didn't have a computer to help me locate deals. If I had it to do over with the knowledge I have now I would have kept her on raw.
The diet Bella is on now is a great food, so if you're keeping her on kibble that one should be no problem.
