My golden used to have chronic yeast infections of the ear. All commercial and Rx. tried over the years. He ended up developing allergic reactions and sensitivities from continued usage from most.
My Vet. started him on "blue brew" mixture of isopropyl alcohol, boric acid, and GentIan violet. After I started to use it his ear infection cleared like magic. He never had another ear infection. I would use it once a week as a preventive measure and after he went swimming.
Website that has the recipe is
ItsForTheAnimals.com. Then click on the blue power ear treatment. Then click on the (genuine) blue power ear treatment link.
I hope this help. My yorkies have never had one ear infections.