[anonymously]

Her symptoms may or may not be food related.
Allergies tend to get worse with age. My dog does best on Nutrisca Salmon and Chickpea (dry and canned) check Chewy . com.
Although her allergies are environmental. My dog may also have some food sensitivities.
Check the search engine here (type in allergies), you may find some tips:

Intradermal Skin Tests http://www.allergydogcentral.com/2011/06/30/dog-allergy-testing-and-allergy-shots/
“An intradermal skin test involves the injection of a small amount of antigen into your dog’s skin. This procedure is most often performed by a veterinary dermatologist or pet allergy specialist”.

http://skeptvet.com/Blog/2011/09/integrating-myths-and-nonsense-with-standard-advice-for-allergic-pets/ (excerpt below)
Bottom Line
Allergies are a serious medical problem that causes a great deal of suffering for pets and their owners. Causes are complex and involve both genetic, developmental, and environmental factors, and symptoms tend to come and go unpredictably, which makes evaluating the effects of any particular intervention challenging. While there are many safe and effective therapies that can help manage allergy symptoms, there is no cure. Only complete avoidance of the antigens the individual is allergic to can eliminate symptoms entirely, and this is often not possible. No treatment that has any benefit is completely without risks, and the risks and benefits must always be carefully and rationally weighed.