Itchy ears aren't only confined to humans -- dogs and cats can have ear itches too.
In the case of a cat or dog with an itching ear, your first move should be to look for fleas or other pests. If they're clean, then you may want to look for an ear infection of some kind.
This is especially true in the case of dogs with ear itches, because a dog's ears can easily get infected from washing. To avoid this situation with your dog, make sure to always dry out your dog's ears after you wash them, or, even better, swab them out with a little alcohol.
If your dog or cat shows persistent signs of ear itching, you need to take them to the vet -- it can be a sign of a more serious condition, so get them checked out as soon as possible.