I don't have a poodle, but have a dachshund who had the same itching problem.

We tried benedryl and prednisone. After a while, both stopped working. So our vet took blood and had it tested at Heska (in Colorado). We found out he is allergic to dust mites and flea saliva. After the initial course of treatment, he now gets maintenance shots on a regular basis. He also gets a different anti-histamine too. He still itches, but not nearly as bad.

Hope your little one gets better soon!