My 5 month old Himalayan rabbit has white gooey discharge from his left nostril. We took him to a vet two weeks ago and she prescribed him some medicine for Pasteurella, although she was not sure this is what he had. We took him off the medicine three days ago and I cleaned his cage, yet today his gunk has come back! His eyes and ears are clear and he's energetic like always. Could he have allergies?