Ear problems can be so darned frustrating to deal with, primarily because they are so prone to recurrence. Part One of this series focused on the anatomy of the canine ear canal. If you haven’t had a chance to read this I encourage you to do so. Observing the length and slope of the external ear canal will help you understand why dogs are prone to otitis externa (inflammation in the external ear canal) and why it can be difficult to treat.
Why is it that some dogs go through an entire lifetime without a single ear problem, yet others become lifelong repeat offenders? Here are some predisposing factors:
Allergies are commonplace in dogs. Some develop allergies to food ingredients, others to environment allergens such as dust, pollens, and molds. While most allergic dogs have itchy skin, some experience inflammation within the ear canals as their only symptom. This inflammation causes production of excess cerumen (ear wax) which happens to be an ideal culture media for the growth of yeast and bacterial organisms.
Identifying and appropriately treating the underlying allergies are necessary to eradicate the chronic ear problems they cause. Doing so may involve a hypoallergenic food trial (strict adherence to a novel protein diet for six to eight weeks) or specific testing to identify which environmental allergies are at play (skin testing preferred to blood testing).
Underlying diseases that affect the skin
The lining of the ear canals is truly an extension of the skin, so it makes sense that diseases that cause skin inflammation may have the same effect on the ear canals. As discussed above, allergies are a classic example. Other diseases that can affect both skin and ears include seborrhea, autoimmune diseases, mites, and hormonal imbalances such as diabetes, hypothyroidism (inadequate production of thyroid hormone), and Cushing’s disease (overproduction of adrenal gland hormones). Treatment of the underlying primary disease is the best bet for resolving the ear problems.
Moisture within the ear canal
Small numbers of yeast and bacterial organisms reside within the normal ear canal. Add moisture to the mix and the populations of these microorganisms can multiply resulting in infection.
When water enters the ear canal it tends to stay put, thanks to gravity working in conjunction with the length and slope of the ear canal. No matter how much head shaking occurs or how many cotton balls are used to soak up the surface water, that ear canal is going to stay wet following swimming and bathing.
The options for dealing with this situation are to prevent the ear canals from ever getting wet (you try suggesting this to someone with a Labrador and a backyard swimming pool), or the consistent application of “drying agent” into the ear canals after they get wet. Ask your veterinarian for a product recommendation. The recipe for a homemade drying agent consists of one part white vinegar, one part water, and one part 70% isopropyl alcohol (avoid the 90% variety). Please do not use this concoction in your dog’s ears before discussing it with your veterinarian.
Gently place a wad of cotton balls within the opening to the external ear canals prior to bath time. Once they are place coat the outer surface of the cotton balls with some petroleum jelly to help repel water. Be sure to remember to remove them when bath time is over!
A growth or foreign body within the ear canal
Any time normal anatomy is disrupted by something that shouldn’t be there, infection is likely to result. The ear canal commonly responds to the presence of a mass or foreign body in this fashion. This is one of the reasons it is so important for a veterinarian to visually inspect the entirety of an infected ear canal using an instrument called an otoscope. Removal of the mass or foreign body is the key to treating the secondary ear infection.
Narrowed (stenotic) ear canals
The normal ear canal is a wide-open structure. When narrowed, it prevents normal air circulation and predisposes to accumulation of waxy discharge. Both of these factors create the perfect storm for infection to occur. Some dogs are born with stenotic ear canals. For others narrowing is a sequela to chronic inflammation that causes thickening of the tissues lining the ear canal. In severe cases, surgical revision to “open up” the ear canal may be necessary.
Are you wondering why I did not add “hairy ear canals” to this list of factors predisposing to canine ear disease? In the good ole’ days we used to torment dogs by stripping the hair out of their ear canals thinking this would prevent infection. Now we know that doing so actually creates inflammation that can then lead to infection. With rare exception, hair removal from the ear canals is a big “no-no”.
Stay tuned for Part Three of this series in which I will review specific diseases of the canine ear canal and their treatment. We’d love your comments and feedback!
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Spot’s Blog: http://www.speakingforspot.com/blog