A dog ear infection often shows up as redness, swelling, or discharge inside the ear canal — this can be dark, yellow, or chunky depending on the type of infection. You may also notice a bad smell coming from the ear. On the outside, your dog might be shaking their head frequently, scratching at the ear, or rubbing their face on the floor. The fur around the ear can thin out from repeated scratching, and the ear flap may look inflamed or have scabs along the edges. In chronic cases, the skin inside the canal can thicken and the opening may appear narrowed.