Allergy testing would be well worth the money especially if he is so itchy that he has sores (ouch). Benadryl may help, check w/ your vet for the proper dose. If it does help it is probably allergy related. I would reccomend a second opinion as well as allergy tests. Have you tried specialty allergy foods? Even though you change the food it may have the same ingredient that is causing him to be itchy. Also you may not see improvement from the food until at least 4-6 weeks after the change sometimes it takes up to a 4 months before showing improvement. Does he have more trouble during a certain time of year or when he is around something? I know it may be hard to remember but did anything change when he first started showing symptoms? Does a specific medication help but then the problem returns after he is finished w/ it? If so he may need a stronger &/or longer dose. Does he have dry skin? Maybe he needs more fatty supplements? It may have origonally started as a problem and turned into a habbit (ussually due to boredom or because he gets attention when he scratches & chews). There are many many different oral meds, shampoos, topical sprays, powders etc. made for skin problems. I wish you luck! Keep us posted!