Otitis externa: Not just an ear problem
Otitis externa (outer ear infection) is an inflammation of the auditory canal. It is one of the most frequently seen problems in dogs. In many cases, ear disease becomes chronic and can be a difficult, frustrating problem to deal with. There are four components that must be addressed in order to achieve the best control possible. These include primary and secondary causes and perpetuating and predisposing factors. Patience and persistence are needed in most cases.
The ear is made up of three main parts, the external, middle and inner ear. External ear infections involve the pinna (ear flap) and the ear canal. The ear canal is 5-10 cm in length and leads to the ear drum (tympanic membrane) and middle ear. Normal functioning ears produce wax (cerumen) which lines the surface of the canal and migrates up and out the ear. In dogs with underlying diseases, this function does not occur correctly and contributes to disease.
Primary causes of ear disease are the actual inciting agents that directly damage the ear canal skin. They can exist alone or in combination with other factors. The most common primary causes of ear disease are allergies, food allergy, and metabolic disorders. Foreign bodies such as plant awns and ear mites are also primary causes of disease.
Secondary causes do not create disease in a normal ear, they only cause problems in the abnormal ear. They are usually easy to eliminate once identified and if they become chronic it is only because the primary problem is not adequately addressed. Common secondary causes of ear disease include bacteria and yeast.
Perpetuating factors in ear disease are changes in the anatomy and function of the ear that occur because of the otitis externa. They are subtle at first but become a main reason for the ongoing chronic disease. These can include things such as excess production of debris, ear canal swelling and stenosis (closure of the canal), rupture of the ear drum, and middle ear infections.
Predisposing causes include excess hair in the ears, droopy ears, high heat and humidity in the environment, water in the ears, tumors, immune suppression, trauma to the canal from overzealous cleaning and systemic disease.
Signs of otitis externa include wet, swollen, red or ulcerated ear pinna. Crusts and brown or pus-like discharges may be present. These discharges often have an objectionable odor. If the condition has been present for quite some time, the lining of the ear may appear thickened and tough and there may or may not be a discharge. Otitis externa is painful and irritating. Often the dog will paw his ear, shake his head, rub the ear along furniture or the floor and scratch the pinna until it is raw.
Diagnosis of ear disease involves a complete physical exam and history, otoscopic exam of the ears, ear cytology (looking at debris under the microscope) and possibly culture of the discharge. In long-standing cases, anesthesia may be required to perform further diagnostic testing such as skull x-rays, biopsies and deep cultures.
Treatment of ear disease includes ear cleaning, both in-hospital and at home. In some cases, this may require sedation initially. We will demonstrate appropriate cleaning techniques for you to do at home. Appropriate medications will be selected to treat any bacterial or yeast organisms that are present. Most cases of otitis externa require a few weeks of treatment. If medication is dispensed, it should be used exactly as directed. After applying the medication into the ear, gently massage the outside of the ear, especially at the base of the ear where the horizontal canal is located.
Along with treatment of the ear infection itself, any underlying primary causes need to be addressed. Testing for thyroid disease, diagnosing any food allergies and/or having allergy testing performed are all under consideration in cases of chronic otitis. Treatment of any diagnosed underlying problems is crucial to long-term success. Failure to address the primary problem will lead to ongoing disease.
One of the most important parts of dealing with otitis, is the need to follow through with progress examinations. As mentioned before, many cases become chronic in nature and will not be cured with just a bottle of medication. Dealing with predisposing and perpetuating problems requires close monitoring of the healing process. Some cases of otitis will clear after just a few weeks, others will take months. In some severe cases, the problem will exist indefinitely, thus necessitating surgical resolution.
Preventing ear problems in dogs is possible in some cases. Excessive ear wax should be cleaned with Epi-otic or another appropriate ear cleaner on a regular basis to remove dirt and wax accumulations. Enough cleaner should be used to almost fill the ear canal and the outside of the ear should be gently massaged. Cotton balls or gauze can then be used to dry the ear. Do not use Q-tips as they usually only push discharges further down into the canal.
If your dog has excessive hair in the ear canal, then it will probably help to pluck this hair every few weeks. Grip the hair with your fingers or a tweezers and pull out with a sharp movement. Most dogs tolerate this well if you do it quickly and routinely. Do not irritate the ears or pull on hair that does not come out readily. Sometimes hair has to be clipped out rather than pulled out. Usually only poodles and terrier-type dogs require ear hair removal.
Before bathing a dog it is advisable to put cotton in the ears, because moisture in the ears sets up a condition that can eventually lead to an infection. Another good preventative is to put cotton in your dog’s ears when you are taking the dog through countryside that has objects that may get into the ear canal. Be sure to remove cotton after the bath or walk as the cotton itself can cause problems if forgotten in the ears. Dogs that swim on a regular basis should have their ears cleaned at the end of the day. Excess moisture can contribute to ear disease.