Yeast vs. Bacterial Ear Infections in Dogs: Key Differences

The symptoms of yeast vs. bacterial ear infections in dogs can look similar. Learn the key differences and how veterinarians treat these types of infections in our canine companions.

Jul 08, 2024·15 min read
Yeast vs. Bacterial Ear Infections in Dogs: Key Differences

Ear infections in dogs are extremely common. In fact, ear infections are one of the most common types of infections seen in dogs and can result in significant discomfort to your furry family member.  

But how can you tell the difference between yeast vs. bacterial ear infections in dogs?  

While many of the clinical signs are similar, it is important to distinguish between the two in order to determine the underlying cause, the most effective course of treatment, and options for prevention. 

Understanding Ear Infections in Dogs 

Ear infections in dogs can be very painful and uncomfortable. A dog’s uniquely “J-shaped” ear canal tends to predispose them to more frequent ear infections than their human counterparts.  

Dog ear infections typically involve the external (or outer) ear canal. This type of ear infection is known as otitis externa.  

There are two other types of ear infections that can affect your canine companion:  

  • Otitis media: infection of the middle ear 
  • Otitis interna: infection of the inner ear. 

Because otitis externa is the most common type of ear infection in dogs, that is what we will focus on in this article.  

A dog’s ear canal normally contains both yeast (a type of fungus) and bacteria. However, when there is an overgrowth of one or both of these organisms, an ear infection may occur.  

An overgrowth of yeast and/or bacteria in a dog’s ears happens when the environment within the ear canal is altered and a secondary infection takes hold. This can happen due to: 

  • Allergies (to certain types of foods or allergens in the environment) 
  • A dog’s ear conformation (i.e. long, floppy ears) 
  • Foreign bodies present in the ear canal 
  • Hormonal conditions like hypothyroidism 

If the underlying cause is not addressed and the ear infection is not treated appropriately, it can become a chronic problem that may lead to more serious complications such hearing loss or ear hematomas (a painful swelling of the dog’s ear flap as a result of frequent head shaking). 

Yeast Ear Infections in Dogs 

The majority of yeast, or fungal, ear infections in dogs are caused by an overgrowth of Malassezia pachydermatis. Small numbers of this organism are normally found within the ear canal of dogs, but several factors can alter the environment and make it more favorable for overgrowth and secondary infection.  

Yeast thrive in moist, humid environments, so dogs with long, floppy ears (think Basset Hounds) or dogs that are frequent swimmers are much more likely to develop yeast ear infections.  

Causes  

Underlying conditions such as allergies — whether to foods or substances in the environment — are a relatively common cause of yeast ear infections in dogs. 

Other chronic or hormonal conditions like diabetes, hypothyroidism (low levels of thyroid hormone), and Cushing’s disease can also promote overgrowth of yeast in a dog’s ear canals.  

Finally, treatment with antibiotics can sometimes eliminate the “good” bacteria, resulting in an imbalance in the dog’s body and an overgrowth of yeast that can extend to the ears and cause a yeast ear infection. 

Symptoms 

Signs of yeast ear infections in dogs are similar to those of bacterial ear infections and include the following:  

  • Excessive scratching of the ears or rubbing them against surfaces 

The ears usually appear red and inflamed and also normally contain a thick, dark brown or black, waxy discharge. Tilting of the head and increased ear sensitivity may indicate pain or discomfort as a result of the ear infection. 

Diagnosis 

Diagnosis of yeast ear infections in dogs is accomplished by taking a thorough history, performing an otoscopic examination, and then examining a sample of the material from the dog’s ear canal under a microscope (known as cytology). 

Your veterinarian will first take a complete history to determine if there are any underlying causes such as allergies that need to be addressed. An otoscope that provides light and magnification will be used to visualize your dog’s ear canal for any foreign material and evaluate the eardrum for any tears. A sample from your dog’s ear canal will be taken for cytology to confirm the presence of yeast and determine the most effective treatment.  

Additional diagnostics such as bloodwork or skin testing may be recommended to test for underlying causes like hypothyroidism or allergies. 

Please note that if your dog’s ears are extremely painful and are unable to be examined by your veterinarian, sedation may be necessary. 

Treatment 

Once your dog has been diagnosed with a yeast ear infection, your veterinarian will likely recommend a combination of the following to treat and eliminate the infection. 

Use an antifungal cleaner: First, the affected ear(s) should be gently and thoroughly cleaned using a veterinarian-approved, antifungal ear-cleaning solution. Cleaning the ears is important for removing the discharge from the ear canal so that treatment will be more effective.  

Topical and/or oral medication: Most yeast ear infections in dogs respond to topical ear medication that contains an antifungal medication to eliminate the yeast and a topical steroid medication to reduce the inflammation and irritation in the affected ear(s). These topical medications may require once-daily treatment for 7-10 days or may be a one-time-only treatment that is applied in the veterinary clinic. If the ear infection is severe or chronic, your veterinarian may also recommend a course of oral antifungal medication. 

Manage underlying causes: Finally, addressing and managing underlying causes such as allergies will be extremely important for resolving and preventing yeast ear infections in your dog. 

Bacterial Ear Infections in Dogs 

The majority of bacterial ear infections in dogs are caused by an overgrowth of the bacteria Staphylococcus spp.  

Other types of bacteria that are commonly associated with bacterial ear infections include:  

  • Pseudomonas 
  • Proteus 
  • Enterococcus 
  • Streptococcus 
  • Corynebacterium 

Staphylococcus and Pseudomonas bacteria can be especially difficult to treat due to the production of a characteristic “biofilm” (a slimy layer of bacteria that adheres to the surface of the ear canal) that results in resistance to many medications. 

Causes 

Similar to yeast ear infections in dogs, bacterial ear infections are often the result of underlying causes such as allergies (food or environmental allergies), hormonal diseases like hypothyroidism, and masses or foreign bodies present within the ear canal.  

Other factors including excessive hair in the ear canals (think Poodles), cleaning the ears too often, and humid environments also predispose dogs to bacterial ear infections. 

Symptoms 

Symptoms of bacterial ear infections in dogs are very similar to those mentioned above in dogs with yeast ear infections, with a few key differences.  

For example, bacterial ear infections typically cause a purulent (pus-like) discharge that is white, yellow, or greenish.  

While both types of ear infections result in a foul odor emanating from your dog’s ears, bacterial ear infections tend to result in a more putrid odor.  

Excessive scratching of the ears, frequent head shaking, and redness are present in both types of ear infections, and owners should be aware that their dogs may be more irritable or even painful when it comes to handling or attempting to clean the affected ears. 

Diagnosis 

Again, the diagnosis of bacterial ear infections in dogs is very similar to that of yeast ear infections. Obtaining a thorough history to identify underlying causes of the ear infection, examination of the ear canal and eardrum with an otoscope and performing cytology on a sample of the discharge from your dog’s affected ear canal are of the utmost importance when determining the cause and most appropriate treatment for bacterial ear infections. Cytology also helps monitor your dog’s response to the chosen therapy.  

In cases of more chronic or resistant bacterial ear infections, a sample of the discharge may be collected and sent to a veterinary diagnostic lab for bacterial culture and sensitivity. This test not only identifies the bacteria responsible for causing the infection but also determines which antibiotics are going to be most effective for eliminating the infection.  

More advanced imaging like CT scans or MRIs may be recommended for chronic bacterial ear infections or middle/inner bacterial ear infections.  

Treatment 

If your dog is diagnosed with a bacterial ear infection, your veterinarian will recommend a combination of the following to treat and eliminate the infection, very similar to what is recommended in the case of a yeast ear infection. 

Use an antibacterial cleaner: The affected ear(s) should first be gently and thoroughly cleaned using a veterinarian-approved, medicated ear-cleaning solution that contains an antibacterial solution. This should be done before applying medication and then every one to two weeks for routine maintenance and prevention of future ear infections. 

Antibiotic medication: Most simple or first-time bacterial ear infections in dogs respond to topical ear medication that contains an antibiotic to eliminate the bacteria and a topical steroid medication to reduce redness and inflammation of the affected ear(s). These topical medications may require a once-daily application for 7-10 days or may be a one-time treatment that is applied in the veterinary clinic. 

If the ear infection is severe or chronic, your veterinarian may also recommend a course of oral antibiotics. Dog owners should be aware that treatment may be necessary for an extended period of several weeks or more. 

Manage underlying causes: Addressing and managing underlying causes such as allergies remains extremely important for resolving and preventing bacterial ear infections in your dog. 

Key Differences Between Dog Yeast and Bacterial Ear Infections 

Now that you have a good handle on yeast and bacterial ear infections in your furry friend, let’s review the key differences between the two types: 

Yeast Ear Infection Bacterial Ear Infection
Underlying causes Allergies 
Hormonal diseases 
Excessive ear moisture 
Use of antibiotics 
Allergies 
Hormonal diseases 
Excessive ear moisture 
Foreign objects 
Ear masses 
Ear trauma
Causative agent An overgrowth of Malassezia pachydermatis An overgrowth of Staphylococcus, Pseudomonas, Proteus spp., etc. 
Ear discharge appearance Dark brown/black, waxy discharge Pus-like discharge that is white, yellow, or greenish 
Ear odor A sweet, musty, or yeasty smell A foul or putrid odor 
Irritation and scratching Yeast ear infections tend to cause more irritation which results in more intense and continuous scratching. Bacterial ear infections will still cause redness, inflammation and scratching. But will typically not cause as much irritation as yeast infections.

Dog Breeds Prone to Ear Infections 

While ear infections can affect dogs of any age, breed, or sex, some breeds do tend to be more frequently affected.  

Breeds with long, floppy ears such as Basset Hounds, Labradors, Beagles, Cocker Spaniels, and Golden Retrievers are at a significantly higher risk of developing otitis externa than their counterparts with erect ears like Chihuahuas and Yorkshire Terriers.  

Due to the anatomy of their folded, floppy ears, air does not circulate as well and moisture — which yeast and bacteria thrive on — gets trapped within the ear canals.  

Other breeds such as Poodles and Schnauzers that naturally have excess hair present within the ear canals are also predisposed to more frequent ear infections due to the trapping of moisture and debris.  

Finally, those dogs affected by chronic, underlying allergies or dogs whose lifestyle includes frequent swimming, may be more likely to develop yeast and bacterial ear infections. 

Preventing Ear Infections in Dogs 

Now that we have examined the most common causes, diagnosis, treatment, and key differences between yeast and bacterial ear infections in dogs, let’s take a look at prevention.  

These tips can save your furry family member from having to experience significant irritation and discomfort. 

Regularly inspect and clean your dog’s ears: This step is key when preventing ear infections in your pet. Make a daily inspection of the ear canal part of your routine when petting or brushing your dog. Evaluate for redness, increased sensitivity, odor, and visible discharge.  

Cleaning your dog’s ears regularly is also important and can be done at home. It is recommended that cleaning be performed if you notice an abnormal discharge or odor, if your dog is prone to ear infections, or if your dog regularly swims or engages in other similar activities. When in doubt, you should always consult your veterinarian as to whether or not you should be cleaning your pup’s ears regularly. 

Cotton-tipped applicators should NEVER be used due to the increased risk of trauma to the ear canal or perforation of your dog’s eardrum. Use cotton or gauze pads for dog ear cleaning.   

Manage allergies and underlying health issues: Food and environmental allergies, or atopy, are the most common causes of yeast and bacterial ear infections in dogs. If your dog seems to have recurrent ear infections, discuss the possibility of underlying allergies and possible diagnostics and treatment options with your veterinarian.  

In addition, underlying medical conditions such as hypothyroidism can make dogs more susceptible to developing ear infections as well as other skin conditions. The majority of these conditions can be effectively managed with daily medication or diet and lifestyle changes. Scheduling regular check-ups with your veterinarian is the best way to detect and manage these conditions. 

Keep ears clean and dry: Because yeast and bacteria thrive in moist environments, it is important to thoroughly dry your dog’s ears after bathing, swimming, or any other type of water-related activities. Placing cotton balls in the opening of the external ear canal before bathing can also help to prevent water from entering your dog’s ear canal — just don’t forget to remove them afterward! 

Do your dog breed research: As discussed previously, certain breeds of dogs (i.e. those with long, floppy ears!) are prone to developing more frequent ear infections. While this shouldn’t deter you from choosing a particular breed, you should be aware of the possibility of increased care and financial responsibility that might be associated with dog breeds prone to allergies and ear infections. Owners should also be aware that breeds like Poodles will require regular grooming by a professional groomer to remove excess hair from the ear canals to prevent yeast and bacterial ear infections. 

Schedule regular check-ups with your veterinarian: This is one of the most important factors for preventing yeast and bacterial ear infections in your canine companion. Scheduling an appointment with your veterinarian as soon as you notice any excessive scratching, redness, abnormal discharge, or increased sensitivity or discomfort in your dog’s ears will reduce the severity of the infection and the amount of time it takes to resolve the ear infection.  

On the flip side, it is also important to schedule a recheck with your veterinarian to ensure the chosen treatment is effective and the yeast or bacterial ear infection is completely resolved.  

Conclusion 

Yeast and bacterial ear infections in dogs are prevalent. Chances are that your dog will encounter at least one in its lifetime. Early recognition of signs such as excessive head shaking or scratching of the ears, redness, odor, abnormal discharge, or increased sensitivity is key for effective treatment and resolution of yeast and bacterial ear infections in dogs.  

While there are certain key differences between yeast and bacterial infections in dogs that you as an owner may be able to distinguish, it is best to consult your veterinarian to obtain an accurate diagnosis and determine the most effective treatment.  

In addition to regular ear care, your veterinarian will be able to provide the best strategies for the prevention of future ear infections so your furry family member can live his or her best life free from irritation and discomfort. 

Jennifer Rowan-Hitchcock, DVMJ
WRITTEN BY

Jennifer Rowan-Hitchcock, DVM

Dr. Jennifer Rowan-Hitchcock is a dedicated veterinarian who aspires to use her veterinary knowledge to educate and empower pet parents. She received her Doctor of Veterinary Medicine degree from Kansas State University and veterinary medical acupuncture certification from CuraCore VET. She is the owner/operator of Spotted Tail Mobile Veterinary Care.

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The information contained within this site is not intended as a substitute for professional medical or veterinary advice. PetLab Co. is not intended to diagnose, treat, cure or prevent any disease. If your pet has, or you suspect your pet has any medical condition, you are urged to consult your veterinarian. Medical conditions can only be diagnosed by a licensed veterinarian. These statements have not been evaluated by the Food and Drug Administration. Results May Vary. Not intended for human consumption. Please consult your veterinarian regarding any change in treatment or supplementation.
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