The idea that raw is the fix all often does not work for truly alllergic and/or ensisitive dogs. Ome dogs yes, so might work, but don't get lulled into thinking it will cure all.
Also, most dermatologists cannot tell you what foods your dog is allergice to, as most only use allergy tests for environmental allergies, not food allergies. They will have you do food trials in an organized way to determine food allergies and senitivities.
I work with my regular vet and use the Spectrum food and env allergy panel, which has helped 3 out of 3 of my dogs. Dermatologists will nearly all the time tell you that they do not work, which I disagree with.
Also, many environmental allergies will cross react with foods and cause sensitivities. Ragweed allergies very often do this, often causing problems with raw citrus. It can get quite complicated when you delve into it deeply.
Some dogs just don't do well with certain carbs or starches, and they are not technically allergie.