Head shaking, pawing or scratching at the ears, odor, brown discharge, and redness or swelling inside the earflap indicate an infection. This may be caused by injury or by foreign bodies in the ear (ticks or plant matter from running through high grass), by bacterial or fungal infections or by mites. Flop-eared dogs are very pronto this ear infection, particularly cocker spaniels. In my dog-grooming days, I don't think I ever groomed a cocker with healthy ears. Fungus infections inside the ear can be caused by leaving bath water inside them, or from too many treatments with antibiotics. Chronic ear infections that are bacterial or fungal are signs of a reduced immune system and may also come from food allergies.