[anonymously]

excerpts from: http://www.2ndchance.info/Apoquel.htm
Food Allergies are probably over-diagnosed in dogs (they account for, perhaps 5-10%). Hypoallergenic diets are occasionally, but not frequently, helpful in canine atopy cases but you should always give them a try. Food intolerances are more common – but considerably more likely to result in digestive disturbances and diarrhea than in itching problems.

http://www.2ndchance.info/allergytesting.htm
Skin tests to determine what your pet might be allergic to are considerably more accurate, on the whole, than blood tests. However, they are not 100% accurate either. To have them performed, you will need to locate a board certified veterinary dermatologist
http://www.acvd.org/