Nice to meet you!
I can try to help, but just to get a little more history...
Which foods have you tried?
Is your dog currently on a flea preventative, and if so, which one?
What meds has he been prescribed so far?
Is he always itchy like this, or does it become worse at certain times of the year?
There are a lot of things that can trigger skin problems. Food allergies, pollen allergies, and flea allergies are the most common ones. My yorkie has seasonal pollen allergies, and I have a cat who is allergic to almost everything out there, so I've got some experience dealing with these issues in my own animals.