What's the matter with a dog constantly scratching its ears and shaking its head?

A dog constantly scratching its ears and shaking its head may have the following reasons:

Ear mite infection: If a dog's ears are not cleaned regularly, they are prone to dirt and severe cases can lead to ear mites. This causes itching in the dog's ears, leading to constant scratching and shaking of the head. Additionally, the dog's ear canals will have a large amount of dry, dark brown matter and a bad smell. It is recommended to take the dog to a pet hospital, perform a microscopic examination of the earwax, and clean the ears early if there are ear mites. Treatment with medications specifically designed for ear mites should then be administered.
Malassezia infection: When a dog is infected with Malassezia, it can cause itching in the ears, leading to constant scratching and shaking of the head. The dog's ears will also show signs of thickening, smelling bad, and becoming red and swollen. It is advised to take the dog to a pet hospital as soon as the above symptoms are noticed, and if the infection is confirmed, treat it with antifungal medications.
Ear inflammation: When a dog has ear inflammation, it may scratch and shake its head frequently due to itching and pain. The ears will also be red, swollen, and may have scales or pus. In this case, it is necessary to clean the dog's ears and then use medications specifically designed for ear inflammation. Simply drop the medicine into the ear canal.
Long ear hair: Some dogs have long ear hair that constantly stimulates the ear wall, causing discomfort and leading to constant scratching and shaking of the head, especially in breeds with long hair such as Poodles, Bichon Frisés, and Schnauzers. If you notice that your dog has this problem, it is best to take it to a professional pet hospital to have the ear hair removed to avoid hurting the dog. Removing the long ear hair allows the ear canal to remain airy and dry, reducing the likelihood of bacterial and parasitic proliferation.