Ear infections in dogs and cats
You may notice a foul odour emanating from your dog or cat’s ears, or maybe the pinnae (ear flaps) are red and warm, or you can see a dark discharge (or pus) or inflamed ear canal. However, it would be your pet’s behaviour that alerted you to the potential problem to begin with: persistent scratching, head-shaking, pawing at their ears and/or vocalising while rubbing their ears. They may flinch when being touched on the head or even avoid your touch altogether. 
Ear infections may occur in the outer ear (otitis externa), the middle ear (otitis media) or inner ear (otitis interna). In this article, we’ll explore outer ear and middle ear infections, which are more common reasons for pet owners to bring their pets in to see the vet, and are more frequently diagnosed than inner ear infections.
Let’s examine the signs of ear infection, what could possibly cause ear infections, how they are diagnosed and what the treatment options are for ear infections in dogs and cats.
What are ear infections?
Ear infections in dogs and cats are a very common pet complaint. Something will change the ear’s environment, which allows for a pathogen to take hold, multiply, and cause the infection. An infected ear will be warm, swollen, painful and full of debris, causing behaviour changes in the dog or cat. The infection usually occurs in the ear canal, which is part of the outer ear (thus diagnosed as ‘otitis externa’). If it is treated, it will not have the opportunity to infect the middle ear. However, if an ear infection progresses unchecked for too long, it can extend into the middle ear, causing otitis media. Otitis media can also be caused by an object piercing the ear drum.
Ear infections can be acute or chronic. Some pets are predisposed to recurring ear infections, such as when a disease is systemic (like an allergy or endocrine issue) and ear infections are a known symptom. In these instances, it’s crucial to identify and treat the disease so that the symptoms (like ear infections) can be reduced or prevented altogether.
What causes ear infections in dogs and cats?
It’s a common assumption that ear infections are caused by bacteria or yeast overgrowth, but the primary cause is a change in the dog or cat’s ear environment. These changes can be the result of simply the shape of the animal’s ear canal, a persistently moist environment (for instance, in a dog who enjoys swimming), side-effects of medication, autoimmune disease, or allergies. When the environment in the external or middle ear is altered, it sets the stage for bacteria, yeast or parasites to move in. The animal’s skin microbiome is unable to keep the pathogens in check, so their overgrowth causes inflammation, ear discharge, redness, foul odour, and a persistent itch. It’s these symptoms that make pet owners realise their pets are uncomfortable and seek help from the vet.
Primary causes of ear infections in pets
There are primary causes and predisposing factors that can set animals up for developing ear infections. These include:
- pets with hairy ears, narrow ear canals, or floppy/droopy ear pinnae – these characteristics can lead to trapped moisture and retained wax; the perfect breeding ground for bacteria
- allergic diseases (such as atopic dermatitis or food allergies)
- auto-immune skin disease
- endocrine disorders (Cushing’s disease or hypothyroidism)
- foreign bodies lodged in the ear
- ear mites (a more frequent cause of ear infection in cats than in dogs)
- a range of other causes relating to the skin health inside the ear
When cats have diseases like feline leukaemia (FeLV), feline immunodeficiency virus (FIV) or diabetes, this can depress their immune system, allowing bacteria and fungi to flourish and cause an ear infection.
Secondary causes of ear infection in pets
When the skin’s microbiome is disrupted, its immune defences are lowered, which can allow pathogens to multiply out of control. These pathogens are the secondary causes of infection:
- fungi/yeast – particularly Malassezia
- bacteria
Sometimes, you may have the best intentions for cleaning your pet’s ears regularly, but the over-cleaning can disrupt the microbiome in their ears and actually cause an infection.
What are the symptoms of ear infections?
Ear infections show up with a range of nasty symptoms. However, not all pets will develop the same symptoms, which is why it’s important to bring your pet to the vet for a proper diagnosis. Pets may exhibit some or all of the following symptoms:
- redness in the ear canal and on the pinnae
- warm ears
- inflammation/swelling
- foul odour
- scratching the ears
- head-shaking (as though trying to dislodge something from the ears)
- display of pain (such as avoiding or ducking) when ears or the top of the head are touched
- dark discharge from the ear canal
- scaly skin in the ear
- growths inside the ears
These symptoms may be present in one (unilateral) or both (bilateral) ears.
How are ear infections in pets diagnosed?
When you bring your dog or cat in for a diagnosis, the vet will ask you for a history of your pet’s symptoms: when did you first notice the odour, heat, scratching, etc? What was your pet doing in the days or hours leading up to the first symptoms? The vet will then perform a complete physical examination before examining the ears. The ear with the least pain and irritation will be examined first. However, if the ears are too painful or inflamed, or the animal resists handling, the vet may need to sedate the dog or cat before examining them. Some pets may need medication to reduce the swelling and inflammation before being examined. In some cases, the vet may recommend that the animal’s ears undergo imaging by X-ray, CT scan or MRI so they can see if there is an obstruction, growth, or other suspected reason for the infection.
Usually, the vet looks inside the animal’s ear with an otoscope to identify the presence of foreign bodies inside the ear canal, wax and other debris that has been compacted, or any damage to the surface of the canal or ear drum. They will take a swab of wax or ear discharge, or perform a skin smear to identify any overgrowth of bacteria or fungi, or identify the presence of mites. Viewed under a microscope, these cultures can tell the vet immediately what kind of pathogen or overgrowth they are dealing with. The vet may also see the presence of skin mites or mite eggs in the discharge, which will reveal the cause of the infection.
How are ear infections treated?
The treatment of the ear infection is always determined by the cause. In cases where ear infections are the symptom of a systemic problem or disease, treating the disease will clear up (or reduce) the recurrence of ear infections. Some diseases are incurable and can only be managed for the rest of the animal’s life (such as allergies, diabetes, Cushing’s disease, hypothyroidism, etc.), so they may experience ear infections from time to time, which also need to be managed.
If the ear infection is severe, the vet will administer pain medication as well as medication to reduce the inflammation and make it more comfortable to clean the ear. Sometimes, the animal may need to be sedated to allow the vet to clean their ears properly. Cleaning the ear (called lavage) is necessary to get rid of the wax, debris and other gunk in the ear canal, as well as to prepare the ear for topical treatment. If the ear infection is exacerbated by the presence of lots of fur in the ears, the fur will need to be clipped before cleaning.
If the infection is the result of bacterial overgrowth, the vet will administer antibiotics; yeast is treated with antifungal medication; mites treated with antiparasitic medication. The vet may also prescribe corticosteroids to reduce inflammation. Treating ear infections is not a quick or simple treatment and it may take some time for the ear environment to return to normal. The vet may want to see the animal once or twice a week while the infection is clearing up, which may take two to four weeks. Severe, recurring ear infections can take up to a few months to clear up, after which regular preventative treatment must be administered – sometimes for the rest of the pet’s life. It is important that pet owners comply with the vet’s advice and are consistent with their pet’s care at home.
How to prevent ear infections in pets
There is a lot you can do to minimise the risk of your dog or cat developing an ear infection. Most importantly, keep the ears clean and dry – especially if your pet has long or droopy ear flaps, if they love to swim, or after a bath. Check their ears regularly for any signs of inflammation, odour, or excessive wax or ear discharge. Remember that cleaning their ears too regularly can also disrupt the microbiome in their ears and cause infection. Ask the vet to recommend the ideal cleaning schedule for your dog or cat’s ears.
If your dog or cat is showing signs of allergic reaction to food, their environment or the season, ask the vet about cleaning their ears as a preventative measure, but to also address the primary allergic condition. It is also important to ensure your pet is comfortable with having their ears touched, especially if they suffer from recurring ear infections and will need to be handled regularly.