Dogs shake their heads when their ears are itchy or there is an irritation there. If your dog is shaking their head repeatedly and the behavior does not stop over a day or so, you should take them to the vets to investigate further.
The most frequent problem that causes excessive head shaking in dogs is an ear infection. Ear infections tend to be itchy and produce a lot of discharge and inflammation. If you lift up the flap of your dog’s ear and see redness, swelling, or discharge, an infection is likely. You should also be aware of how your dogs ears usually smell as they will smell different. Ear mite infestations can cause similar symptoms, but they are not as common as yeast or bacterial infections. Sometimes the infections occur deep within the ear and so are not as obvious upon inspection.
Head shaking may also be due to allergies. There may be other signs that accompany an allergy such as scratching the ears, rubbing their face and sometimes hair loss and chewing their feet.
There are other reasons for head shaking including water in the ear, foreign objects in the ear canal, inflammatory diseases and even neurological disorders. The head shaking may lead to ruptured blood vessels in the ear flap that if serious, may require surgery.