Dog Veterinarian
I am a practicing small animal veterinarian with 13 years experience.
Allergies can cause dogs to be itchy and scratch. Because the ear canal is part of the skin and in a moister environment, sometimes a dog will have irritation in the canal but not be scratching elsewhere. The benadryl won't hurt them (might make them a little sleepy), so it is worth a try.
Dr. Scarlett