[anonymously]

Food sensitivities (food allergies are rare) usually result in GI disturbances, such as vomiting and diarrhea, not pruritus.

In my opinion, a visit to the vet is in order. There are a variety of things that could cause the symptoms you have described. Only a veterinarian that has examined your dog and has done some testing can diagnose.

Use the search engine here and look up “allergies” you may find some helpful information.