Ear infections in Pets

Pet Ear Anatomy

Ear Anatomy
There are many causes and types of ear infections that can occur in pets.  Ear infections may be due to bacteria, fungus, or a mixture of different microorganisms.  There are also other forms of ear disease which can mimic infection.  To better understand why ear infections occur and what you can do to help your pet, let's start by learning about ear anatomy. 

To the left, is an anatomical drawing of a dog's ear (a cat's ear is similarly structured).  Notice that unlike a human's ear canal which is a straight tube, a pet's ear canal is an "L" shape.  This "L" is made up of a "vertical canal" and a "horizontal canal".  Often, an ear disease develops in the horizontal canal, but you may not notice the problem until discharge or swelling progresses into the vertical canal. 

At the bottom of the horizontal canal is the tympanic membrane or "ear drum".  Beyond the ear drum are the delicate structures involved in hearing.

There are three main areas where ear infections to occur:

1. otitis externa- infection of the "external" ear canal (the vertical canal, the horizontal canal, and the ear flap or "pinna").  This is the most common type of ear infection in pets.
2. otitis media- infection of the middle ear (the inner surface of the ear drum, tympanic bulla, and auditory ossicles).
3. otitis interna- infection of the inner ear (causes ear pain but also neurologic symptoms such as head tilt, abnormal eye movements, and incoordination). 

Ear Infection Symptoms
The most common symptoms noted during an ear infection include: 

• Ear scratching or head shaking
• Discharge from the ear which may appear as dark brown, yellow, waxy, mucousy, or bloody depending on the type and severity of infection.
• Bad odor from the ears
• Swelling or redness of the ear flap or vertical canal

Other potential ear disease symptoms: walking with a head tilt or walking in circles, hearing loss, unusual eye movements called "nystagmus", loss of balance, rubbing ears on furniture or floor, hairloss around the ear, etc. 

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Why do ear infections happen?  
This is actually the most important question that you can ask yourself if your pet develops an ear infection.  If your pet has a single ear infection, which clears up readily with treatment, the exact cause of the infection may not be determined.  However, if your pet develops a recurring infection, then further diagnostic testing is needed to discover why this is happening. 

Potential underlying causes for ear infections include:

• Breed predispositions- some breeds such as Cocker Spaniels or Shar-peis have narrow ear canals and excess wax production.  Dogs with ears that hang down or have hairy ear canals may also be more inclined toward infection. 
• Excessive moisture in the ear canal- either from swimming, bathing, or improper ear cleaning.
• Systemic disease- certain internal conditions such as hypothyroidism or Cushing's disease may create an easy environment for microorganisms to grow. 
• Parasites- ear mites or mange mites can lead to secondary ear infections.
• Hypersensitivities- Atopy (environmental allergens which are inhaled), food allergy, or contact allergy
• Foreign bodies- plant material, for example, which may become lodged in the ear canal
• Obstruction of the canal- tumors, polyps, cerumen gland hyperplasia, etc
• Autoimmune diseases
• Resistant bacterial infections

How do I treat an ear infection?
The appropriate therapy for ear infections depends on if an underlying cause can be determined.  Your veterinarian's first step will be to perform an otoscopic exam.  An otoscope allows for a magnified view of the vertical canal, horizontal canal, and tympanic membrane or "ear drum".  This exam will help determine if ear mites, tumors, polyps, or foreign bodies are present.  It is also important to determine if the ear drum is intact or ruptured.  There is potential for certain medications or cleansers to cause ear toxicity if they are allowed to drain into the middle ear through a ruptured ear drum.  

Other tests that your veterinarian may discuss with you include:

• Whole body physical exam- this is an important step for any ear infection.  During a physical exam, your veterinarian will not only be examining the ears, but the entire body for signs of disease that may have lead to the ear infection.  For example, the skin that lines the ear canal is a continuation of the skin on the rest of the body- if your pet is having ear problems, then the entire body should be examined for other skin lesions and vice versa. 
• Ear swab- this involves taking a sample of the discharge in the ear canal, applying special stains to the sample, and then examining it under a microscope.  This test helps determine what microorganisms are present, what medication may be best suited for this type of infection, and to help evaluate the ear for improvement over time. 
• Ear culture and sensitivity- this test is often done if a resistant infection is suspected.  An ear culture is performed by sampling the discharge in the ear and presenting it to a laboratory.  The laboratory will grow the microorganisms from the sample and test them against various antibiotics to help determine which drug is best to use. 
• Bloodwork- checking thyroid hormone level or for other signs of internal disease which may have lead to the ear infection.
• Skin scraping or biopsy to evaluate for mange mites or autoimmune disease
• Imaging- xrays may help detect fluid filled bulla in some pets.  CT or MRI is best suited for evaluating inner ear disease or looking for tumors.  Advanced imaging such as this is done at a referral facility. 
• Allergy testing or food trial

Treatment regiments often include:

• Ear cleaning- your veterinarian will discuss with you the proper technique for cleaning the ears.  How often the ears need cleaned and with what will be determined by the type and severity of infection. 

General tips: ear cleansers should be labeled specifically for pets.  Please do not use a human product as the skin pH is different.  Please refrain from using "home made" cleansers containing alcohol, hydrogen peroxide, or water- these can be irritating to the delicate ear tissues and can leave excess moisture in the canal.  Please DO NOT use cotton tipped applicators ("Q tips") to clean the ear canal- the "L" shape to the canal means that you will pack more discharge deeper down than you will get out.  It is OK to use them in the folds of the ear flap, but not the canal.  We prefer soft material such as cotton balls for cleaning the canals as these are non abrasive. 

• Topical ear treatments- the mainstay of ear therapy is typically a topical medication at the site of infection.  Your veterinarian will discuss proper application of these medications. 

General tips: please follow directions carefully and call your veterinary clinic with any questions.  For many infections, the symptoms may resolve sooner than the duration of treatment, but please DO NOT stop providing the medication early!  Often, the symptoms may disappear, but infection can still be present in the horizontal canal where you cannot see it.  Please keep all recheck appointments that your veterinarian recommends- the horizontal canal needs to be examined to determine if the disease is actually resolved or just improved.  Please do not medicate your pet sporadically with "leftover" drugs- this typically only masks the symptoms of disease and can lead to worsening or resistant infections. 

• Systemic medications- other drugs may be recommended depending on the type/severity of infection or underlying cause.  Examples, of these medications may include: an oral antibiotic, anti-yeast drug, anti-inflammatories, antihistamines, or other allergy therapies. 

Commonly Asked Questions

• My pet gets ear infections all the time.  Why can't I just call in for a prescription of ear medication?      If your pet is suffering from recurrent infections, then he or she deserves an examination to see if a different treatment would work better.  Recurrent infections means that there is an underlying cause that is not being addressed; therefore, repeatedly dumping antibiotics into the ear is not the real answer for the problem.  Your veterinarian may recommend further testing or alternatives therapies. 
• My pet's ear infection seemed better halfway through treatment so I stopped- is that ok?   No.  Cutting treatment short (even if the pet seems better) can lead to recurrent infection later.  Infections that are not treated completely lead to antibiotic resistance.  Please finish all medications as prescribed and talk to your veterinarian if you have any questions or concerns. 
• My pet gets frequent ear infections, so I can squirt in some of the leftover ear medication sometimes to keep it from coming back, right?  No.  Sporadic use of antibiotic drops leads to worsening or resistant infections later on.  Many antibiotic ear medications also contain an anti-inflammatory steroid which may be what is helping your pet feel better (ie. it may not actually be an infection that you are treating).  Talk to your veterinarian about cleaning the ears or using antihistamines instead. 
• What happens if I don't treat the ear infection?  Ear infections are painful!  External ear infections that go untreated can progress to middle or inner ear infections.  Aural hematomas (large blood clots under the skin of the ear flap) can form due to forceful head shaking and scratching.  Chronic ear infections lead to mineralization / hardening of the ear canal and in some pets the ear canal may become so swollen that it closes.  Closed ear canals (called "end stage ear disease") can no longer be treated topically and may need to be surgically removed in order to provide relief from pain and infection. 
• My pet has dark debris in the ear canal- doesn't that mean ear mites?  Not necessarily.  Ear mites do produce a dark, "coffee grounds" debris, but other types of infection can mimic this.  Ear mites are tiny parasites of the ear canal skin and they have to be transmitted from one animal to another by close contact.  Ear mites can be present by themselves or can also appear with a secondary infection.  See our section on ear mites for more information.
• My dog's ears smell yeasty- doesn't that mean there is a yeast infection present?  Not necessarily.  You cannot diagnose the type of infection based on smell alone as any type of infection is going to have an odor to it.  Yeast may be present alone or in combination with another microorganism.  If infection is present, your pet should be examined for an underlying cause. 
• How often should I clean my pet's ears?  This may depend on your pet's medical history.  In general, we recommend cleaning a dog's ear every 1 to 2 weeks for maintenance of healthy ears.  If your pet has a history of ear disease, you might need to clean more often.  Please talk to your veterinarian for recommendations on your individual pet.