Carol
Itching can also be caused by hypothyroidism. You can pay for the whole allergy work-up only to be told your fog is allergic to an extinct fruit at endemic to Atlantis, and then out them on a no-good drug. A trainer who worked with my dog back in 2004 recognized in him the same symptoms that, in her fog, were ultimately diagnosed as hypothyroidism and successfully kept at bay by a common thyroid drug. That was a lovely black lab who seemed to be a Great Dane cross.
Many years later, in 2017, my veterinarian told me there was a new way to deal with itchy ears. My black lab/malamute/chow chow/German shepherd mix had been a recurrent itchy ear patient and I would periodically treat him for whatever the vet said it was as well as get his ears cleaned as needed. The magic new drug was was Apoquel. My dog, age unknown but in glossy, fine form, died of cancer of metastatic cancer of the spleen less than a year later.