I always had excellent results using the Ottomax to clear things up. The problem is keeping the inflammation and subsequent infection from coming back. In my Lab's case I knew it was swimming, and the vinegar+water trick worked... if I remembered to apply it! In some dogs it can be a result of food allergies, but for the most part it's due to excess moisture in the ear.

Once the ear has been massively infected, the ecology of the ear is disrupted, and the infection will readily come back. An unending struggle.

P.S. Per allergies, the yeast growth itself in the ear can cause allergic reactions. Time again for Benedryl.