Not sure if my Bailey's story helps you, but I will tell it in short. It has been more than 9 months ago we had this issue.
He was scratching his whole waking hours; chest, backside and legs. So much so that there were patches of his hair gone
When looking at the back of him, he looked like he was wearing fuzzy short boots
It was so distressing to see him like this, I took him to the vets. The vet suspected an allergy to chicken, so was sent home with some antihistamine meds. and we were on the lookout for new food. A wild animal food was ok I was told, so got some special food with duck. Soon he was back to his biting. I was so upset, then I was told from someone else that anything poultry was not to be given, as it is something in the poultry protein. Made total sense then with the duck. He has been on ZD sensitive food and he got better. Over time he is back to his normal, goofy and sweet self.
Hope that you find out what's bugging your sweetie!!