Since the dogs consume a lot of prepared food materials including various kinds of proteins, fillers, coloring agents and more; in the commercial food materials, the incidences of food allergies are more than one can imagine. Dog allergic reaction to food mostly involve the skin or the gastrointestinal tract.
I use Zincomega (the name in Turkey) it is a syrup vitamin for kids containing zinc and omega3 and omega 6, Vitamin B6 and C. It takes time if the rash is bad but in a month all rash and scratching was gone for my German Shepherd.I had taken her to many vet clinics and none found a solution. Now we have a boston terrier puppy 3 months old. She is fed Acana puppy and I give her 1 cc of Zincomega 3-4 days a week. Our vet ( the new one, who told us to use Zincomega) at the animal hospital said it would be very good for her to use it.In Turkey it is sold at pharmacies. I hope this will help.