Does your dog have itchy ears? Does she shake her head a lot and scratch at the ears? Does he have a bad odor and dark "goop" coming from his ears? If this is your first time having a dog with "bad" ears, there is a better than average chance that you'll think it's ear mites. And if you think that the problem is due to mites, you might go to your local pet supply store, pick up some over-the-counter ear mite medicine, and start using it. You might then be a bit surprised when the problem keeps going on, despite a few weeks of treatment.
Some of you are nodding a bit sheepishly, as you have done this very thing. And I know it happens commonly, because a couple of weeks ago one of the people in my church asked me about this, and I had two clients on Saturday that thought the same thing. Admittedly, it's probably a valid mistake, because the average pet owner is more likely to hear about ear mites than ear infections when talking to other pet owners.
Ear mites do happen, and do cause intense itchiness and debris in the ears. However, they are extremely uncommon in dogs. I have been practicing for almost 12 years, and over that time have seen somewhere between 5 and 10 dogs with ear mites. However, I see dogs with ear infections just about every day, and during the warm parts of the year I'll easily see 5-10 ear infections in one day! In cats the ratio flipped around...itchy ears in cats more commonly indicate mites than infection.
There is no quick, easy way to just look at a dog or cat and tell whether it is mites or an infection. Both problems have identical symptoms, and can have a very similar debris. The ear mites are just barely microscopic, so with good magnification from an otoscope, a vet might be able to see them in the ear canal if there are enough of them. The definitive way to diagnose the problem is to get a swab of the debris from the ears and look under the microscope. Ear mites are very easy to find, and many times you can see the juveniles, adults, and eggs. Infections are just as easy to diagnose, as the bacteria and yeast are obvious with a good stain.
So the next time your dog starts shaking his head, don't automatically assume that it's ear mites. Odds are strongly against this diagnosis, and you should take him to your vet. Once there, allow your vet do to proper diagnostics so that the problem can be quickly treated.