Red, swollen, painful ears, detectable ear odor, and drainage are all signs of possible ear infection and inflammation of the ear canal. These infections are not uncommon, and there are many ways for ear problems to develop. Unlike human ears, an animal's ear canal is deep and curved. Debris, wax, and excess moisture may accumulate. Bacteria or fungus may grow in the ear canal and lead to an ear infection. In addition, foreign objects, such as grass, foxtails, or ear mites can also cause irritation, making the ear more susceptible to infection. If you notice a discharge or odor from the ear, excessive head shaking, or pawing at the ears, you should contact your veterinarian immediately. Delay in treatment of infected ears may result in severe damage to your pet's hearing. For more information on pet ear infections, contact a veterinarian.