A common cause of ear infections in dogs is an allergic reaction to something in the dogs environment or food. With food, the culprit is often an excess of grain and/or sugar. Sugar feeds the yeast naturally present in the dogs body, so when a dog has too much sugar in their diet, a yeast overgrowth occurs, and it can build up in the ears. It can accumulate around the folds of the ears and within the canal. It tends to be a dark reddish brown wax-like substance that has a pungent odor.