Is your cat shaking their head? Is there debris in their ear? Is one or both of their ears red and smelly? Your cat might have an ear infection. Here's everything you need to know about the condition.

Cat Ear Infections: Where Do They Happen?

While humans usually develop infections in the middle or inner ear, outer ear infections are more common in cats. This type of infection affects the pinna — the external part of the ear — and the part of the ear canal outside of the eardrum. In some cases, outer ear infections can cause a perforation of the eardrum and lead to problems in the inner and middle parts of the ear.

Veterinarians classify a cat ear infection by the type of infection that causes it. Cat ears can be infested with yeast, bacteria, ear mites or a combination of all three.

Cat Ear Infection Causes

Ear mites are common mites that live on the surface of pets' ears, including those of cats, dogs and ferrets, says the Companion Animal Parasite Council. Ear mites are very contagious and spread through direct contact. Fortunately, people can't contract ear mites. Because ear mites are so contagious, they're a bigger problem when multiple cats live together in tight quarters, like in a shelter.

While ear mites are generally the main culprit of a kitten ear infection, yeast and bacterial infections are usually seen in older cats. Yeast and bacterial infections in kittens tend to only be secondary to an ear mite infestation.

Ear infections due to yeast or bacteria can develop secondary to an ear mite infestation, or can develop due to allergies. It's normal for small amounts of yeast and bacteria to live in the ear canal, but if something puts the ear out of balance, like ear mites, polyps or allergies, then a secondary bacterial or fungal infection can occur.

Signs of a Cat Ear Infection

Cats normally keep their ears very clean. A normal, healthy cat ear is pink or pigmented, has very little debris and doesn't have an odor. An infected ear looks very different. If your cat is suffering from an ear infection, you may notice any or all of the following:

• Excessive scratching at the ears or shaking of the head
• Lowered ears when they're usually upright
• Ear redness or scratches on the ear
• Ear discharge that's black, dark brown, white, yellow or green
• Odor from the ear
• Head shyness or irritability when you go to pet the ears

Diagnosing a Cat Ear Infection

Your vet will use a combination of physical exam findings and lab exams to determine whether your cat has an ear infection. They'll likely look inside your cat's ear with an otoscope and use a cotton swab to take a sample from your cat's ear. They'll then recommend treatment based on what they find.