Our dog has many allergies. Finally went to see a specialist for them and I did a lot of research myself. Here's a very quick overview of the main things I learned.
1. the Nutriscan test has very poor reviews in the scientific literature, so much so we didn't bother doing it even though insurance would pay for 80% of it
2. blood tests have improved quite a bit from the old RAST and ELISA tests, we did a liquid gold test on our dog
3. intradermal testing is the current gold standard however it is not great for food allergies
4. most common food allergens are beef, dairy, lamb, wheat, corn, rice, chicken, and eggs
Our dog is allergic to beef from our experiences and is allergic to sheep epithelium (intradermal test). This means he is probably allergic to all ruminants. He's also allergic to feathers which means he's probably allergic to all birds (we suspect he's allergic to chicken based on experience and we've had two bad reactions to duck).
Cut out the beef and understand that it can actually take 3 months for a body to calm down after an allergic reaction to food.