What's going on when a dog shakes its ears?

There are several reasons why a dog shakes its ears:

Foreign objects in the ears: If there are foreign objects such as insects in a dog's ears, the dog will try to shake them out.
Water in the ears: If a dog gets water in its ears, it will shake its head to try to get it out.
Ear mites: If a dog is infected with ear mites, it will shake its ears frequently due to itching.
Ear diseases: Frequent ear shaking can also be caused by outer, middle, or inner ear infections.
Foreign objects in the ears: If there are insects or other objects in a dog's ears, take it to a pet hospital for inspection and have the objects removed using an earoscope. Never use a cotton swab to clean the ears yourself, as this can easily damage the dog's eardrum.
Water in the ears: If your dog shakes its head after taking a bath or playing in water, it's likely that water has entered its ears. Help it clear the water by drying the outer ear canal with a soft cloth during the shaking intervals. If the dog is a drooping-eared breed, you can also use ear drops to prevent infection.
Ear mites: Dogs infected with ear mites will shake their ears frequently due to the itching and swelling of the ears, accompanied by a large amount of dark brown secretions. Treat the ear mites as soon as possible. Typically, owners can first clean the ear secretions with ear cleaner, then apply ear mite medication. The dog should recover within one to two weeks.
Ear diseases: If a dog constantly shakes its ears, it could be due to outer or middle ear infections. The dog may also scratch its ears with its paws. Take it to a pet hospital for inspection and treat it according to the diagnosis. For example, if the outer ear inflammation is caused by mites or fungal infections, it usually requires timely cleaning of excess secretions and applying relevant medications. If it's a bacterial middle ear infection, it needs to have excess secretions cleaned out and receive systemic antibiotics.