Your approach of changing or trying a different meat in the dog food is a sound approach. Between the usual chicken, lamb, or duck, fish, turkey you should be able to find something.

If the allergies tend to be more severe in a given season, then you have a contact allergy involved such as leaf mold in the Fall. It was a problem for my previous dog once she hit 7 yrs of age.

In order to relieve any continued itching the common dosage numbers published for benedryl 1-2 mg/lb. The clear gel caps smeared with a little peanut butter or wrapped in cheese are yummy. My prior dog of 74 lbs received 25 mg of Benedryl at night, and 12.5 in the morning. It usually took 3-5 days for the itching to completely stop. If the skin is irritated or red in appearance then there is a good chance you have a staph skin infection, where a short course of Cephalexin should help clear it up.