[anonymously]

You may find this site informative. http://skeptvet.com/Blog/?s=allergies
And:

Dermatology – Common Issues

“Atopic dermatitis is a hypersensitivity or over-reaction to a variety of commonplace and otherwise harmless substances in the environment such as plant pollens, house dust mites or mold spores. Most pets with atopic dermatitis either inhale or absorb their allergens through their skin. Allergy tests are used to identify what a pet is allergic to in their environment”.

excerpt below 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.

Also, via the search engine here: /forums/search/allergies/

BTW: Allergen Specific Immunotherapy does not address food allergies (rare) or food sensitivities. See my posts for more information.