Ear disease, sometimes called otitis by your vet, is very common in dogs. Ear disease rarely goes unnoticed when it is severe. Dogs with ear problems will generally shake their head from side to side, and may be forever stopping to sit down and scratch their ears or rub the side of their head on the ground. In many types of infection there is a smelly discharge or the ear canal may be full of black wax. Sometimes, dogs with sore ears will just sit with their head tilted to one side.
You should never put anything into a dog's ear unless you have been instructed to do so by your vet. Poking cotton wool buds or other cleaning devices into the ear canal can push debris or foreign bodies further down where they can cause serious damage.
Sometimes a dog with ear disease will shake their head so much that they burst a blood vessel and develop a swelling in their ear flap - a haematoma. If this happens your dog will probably need an operation to drain the swelling.