We've had the same problem with Greta, our airedale mix. She's had an ear infection now for the past three months. And she also has food allergies, and I'm not sure whether the two are related or not.

We've switched to Flint River lamb and rice dog food, which is totally natural, no preservatives, no fillers, and has a lot of extra good stuff in it (be warned tho, its expensive!). Her allergies seem to be under control (no more pawing at her mouth and she also used to foam a bit too). And it seems that her ears are getting better too, altho I can't tell whether its from the food or they're just...getting better. We flush her ears twice a day, and were using antibiotics for 3 weeks. The gunk is finally getting less and less.

Our vet says that it can take months for an ear infection to totally clear up and that we'll probably have to continue flushing her ears, perhaps for the rest of her life.