Dog Food Whether or not dog allergy nutritional vitamins work depends on the canine, the allergens that trigger their reactions, and the vitamins themselves. Though vitamins are useful for canines in general, they do not appear to be typically used as a primary line of defense in opposition to allergy symptoms; they will work as an efficient additive. All over-the-counter allergy meds are designed for people, not for dogs. When treating canine allergy symptoms, Zyrtec may be used, however allo...