ALLERGIC OTITIS
What is allergic otitis?
Otitis is inflammation (redness, heat, pain, and swelling) of the ear.
What causes allergic otitis?
There are three basic causes of the allergies: parasites, atopy (allergic reactions
brought on by normally harmless substances like grass, mold spores, house dust
mites, and other environmental allergens), and food.
Allergic otitis is a common disease of the ear canal of dogs. Otitis can be externa
(of the outer ear canal alone), media (involving the middle ear), or interna
(involving the inner ear and associated structures). Unlike ear infections humans
suffer (children, especially) in which the middle ear is typically affected, this disease is one that usually only affects the external ear canal.
The typical disease process is as follows: Irritation to the skin lining the ear canal
causes inflammation, which results in excess wax production and a comfortable
environment for yeast and bacteria (normal residents of the ear canal) to
overgrow. These microbes cause significant itchiness and more inflammation,
which lead to an itch-scratch cycle conducive to self-trauma via headshaking,
pawing, and rubbing of the ears.
Any dog can develop an ear infection regardless of ear shape, exposure to water
(swimming), or the amount of hair inside the ear canal. That’s because the
underlying cause of the irritation that initiates the disease process is typically
allergic.
The most common cause of allergies in our area is flea hypersensitivity. Your
dog or cat may not have visible fleas because when it grooms, it usually eats the
fleas. However, even a few bites can cause significant allergies in some pets.
Environmental allergies (atopy) and food allergies can cause allergic skin
disease, which is a common reason for otitis externa. Allergic skin disease may
also be influenced by the presence of thyroid disease or adrenal gland disease
(Cushing’s disease).
Other less common causes of otitis externa in dogs include:
• Polyps or other growths in the ear canal
• Foreign bodies in the ears, including dirt, sand, or plant material (foxtails and
grass awns)
• External parasites (like ear mites)
The most severely affected patients often get stuck in a cycle of inflammation,
infection, and thickening of the tissues lining the ear canal (fibrosis), which
eventually leads to narrowing of the ear canals, ruptured eardrums, and debris
and infection within the middle ear.
Over time, scar tissue occludes the canals, preventing medications from reaching
the diseased portions of the canal. The occluded canals also prevent the natural
sloughing of the canal’s skin cells, sebum (wax), and hair, which accumulate in
both the canal and middle ear, thereby intensifying the infection.
Considering the potential long-term nature of this condition, allergic otitis is a
frustrating disease for both owners and veterinarians. But for patients, the
disease is much more critical, given that they typically suffer significant pain.
What signs are associated with allergic otitis?
Affected dogs typically experience recurrent bouts of malodorous discharge,
pain, and itchiness. But a significant subset will suffer these symptoms on a
constant basis with no relief from their profound discomfort. Some pets may even
try to bite someone who attempts to touch their ears or head.
The clinical signs of otitis depend on the severity of the inflammation but may
include:
• Shaking the head or rubbing the head and ears on the floor or furniture
• Scratching at the ears
• Discharge from the ears, which can sometimes have a foul odor
• Redness of the ear canal and earflap (the ears may also feel warm when
touched)
• Ear hematoma, evidenced by a grossly swollen earflap
• Aggression whenever the head is approached
Some dogs with severe otitis may cry or groan as they rub and scratch their ears.
Others will scratch so severely that their nails create wounds on the skin around
their face, neck, and ears. If the otitis is severe or chronic, the outer ear canal
can begin to thicken and become deformed. This thickening can make the ear
opening very narrow, so cleaning the ears becomes more difficult. Ulcerations on
the inside of the ear canal can also result from infection and self-trauma.
As mentioned above, otitis that begins in the outer ear canal can ultimately
rupture the eardrum, ending in otitis media and otitis interna. Progression of this
infection into the middle and inner ear can be associated with more severe
clinical signs, including development of a head tilt, incoordination, inability to
stand or walk, hearing loss, and severe, unrelenting pain.
A medical history and physical examination findings can provide valuable
information for your veterinarian when trying to diagnose an ear infection. The
medical history may include trying to determine how long the ear infection has
been going on, whether it has occurred before and whether any other signs of
illness have been observed. Physical examination findings may reveal evidence
of underlying illness, such as thyroid disease and Cushing’s disease.
How is allergic otitis diagnosed?
Diagnosis of otitis is usually based on a history of previous ear infections and
physical examination findings. Redness, inflammation, discharge, and other
changes within the ear will readily indicate the presence of an ear infection.
That’s the easy part. The hard part is finding out a) what kinds of microorganisms
are taking advantage of the dog’s inflamed ears and b) what’s causing the
inflammation in the first place. Determining both a) and b) generally requires
diagnostic testing. In the case of identifying microorganisms, these are the tests
most commonly used:
Microscopy: The most common test used to identify the presence of mites,
bacteria, and yeast is a simple evaluation of the discharge obtained from
the ear under a microscope. Mites are readily identified in this way. With
special staining techniques, yeast and bacteria can also be identified and
their characteristics evaluated.
Culture and sensitivity testing: Testing the debris inside a dog’s ear using
simple microscopy isn’t always enough when the otitis has been stubborn
or severe. Obtaining a sample of the discharge using a sterile swab and
submitting it to a diagnostic laboratory will help determine exactly which
bacteria and/or yeast are present. This information helps veterinarians
devise the ideal drug strategy to treat the infection.
Underlying illnesses leading to the overgrowth of microorganisms will require a
different approach. Here are the most common tests:
Otoscopy: An otoscope is a tool used to help a veterinarian visualize the ear
canal. This is the ideal tool to help identify the presence of an eardrum
rupture, a polyp, or a mass in the ear canal. Unfortunately, most dogs
require sedation — if not anesthesia — before they’ll submit to this kind of
examination.
Thyroid testing: This determines if thyroid disease may be playing a role.
Adrenal gland testing: Tests to explore the possibility of Cushing’s disease are
sometimes required in dogs with otitis externa.
Allergy testing: A blood test can help identify allergens causing the clinical
signs. Once allergens are identified, a solution is formulated so that
injections can be given at home to desensitize the pet to the allergens.
Food trial: Since food allergies are such a common feature in the chronic otitis
landscape, food trials are perhaps even more important than blood
testing. Most food allergic dogs are allergic to the primary protein source
in their food. A food trial’s goal is to change the proteins the patient eats
to those it has never been exposed to before. If the otitis resolves when
the diet is changed, a food allergy may be the underlying cause of the
condition. A 12- to 16-week period in which the diet is restricted is
considered the ideal approach to undertaking food trials.
How is allergic otitis treated?
Treatment of chronic otitis is a multistep process. First, the bacterial and fungal
(yeast) component must be addressed along with the inflammation. The following
strategies are typically used:
• Cleansing the ear canal is always recommended to clear accumulated debris. If the otitis is painful and/or an extensive process, cleansing should ideally
be undertaken with the pet under sedation or anesthesia. Otoscopy is
often recommended as an aid in this process.
• Topical medication tailored to treat the specific bacteria, yeast, or mites present is typically used (these are usually available as either ear drops or ointments). These include antibiotics, antifungals (to kill yeast), anti- inflammatory drugs (like cortisone), and topical anesthetics.
• Systemic antimicrobials (antibiotic given by mouth or injection) are indicated in some cases, such as if the eardrum is ruptured. Ideally, antibiotic therapy
is based on the results of culture and sensitivity testing.
• Systemic anti-inflammatory medications, such as corticosteroids, are
sometimes employed to reduce the pain, redness, and swelling.
Antihistamines may also be prescribed.
How do you prevent it?
The key to preventing allergic otitis is to reduce the pet’s allergies as much as
possible. The cornerstone of that plan is monthly flea control with an effective
flea control medication. Regular checks for internal parasites are important. If
parasite control does not prevent recurrence, food trials and allergy testing often
reduce or completely prevent the return of clinical signs.
Otitis is inflammation (redness, heat, pain, and swelling) of the ear.
What causes allergic otitis?
There are three basic causes of the allergies: parasites, atopy (allergic reactions
brought on by normally harmless substances like grass, mold spores, house dust
mites, and other environmental allergens), and food.
Allergic otitis is a common disease of the ear canal of dogs. Otitis can be externa
(of the outer ear canal alone), media (involving the middle ear), or interna
(involving the inner ear and associated structures). Unlike ear infections humans
suffer (children, especially) in which the middle ear is typically affected, this disease is one that usually only affects the external ear canal.
The typical disease process is as follows: Irritation to the skin lining the ear canal
causes inflammation, which results in excess wax production and a comfortable
environment for yeast and bacteria (normal residents of the ear canal) to
overgrow. These microbes cause significant itchiness and more inflammation,
which lead to an itch-scratch cycle conducive to self-trauma via headshaking,
pawing, and rubbing of the ears.
Any dog can develop an ear infection regardless of ear shape, exposure to water
(swimming), or the amount of hair inside the ear canal. That’s because the
underlying cause of the irritation that initiates the disease process is typically
allergic.
The most common cause of allergies in our area is flea hypersensitivity. Your
dog or cat may not have visible fleas because when it grooms, it usually eats the
fleas. However, even a few bites can cause significant allergies in some pets.
Environmental allergies (atopy) and food allergies can cause allergic skin
disease, which is a common reason for otitis externa. Allergic skin disease may
also be influenced by the presence of thyroid disease or adrenal gland disease
(Cushing’s disease).
Other less common causes of otitis externa in dogs include:
• Polyps or other growths in the ear canal
• Foreign bodies in the ears, including dirt, sand, or plant material (foxtails and
grass awns)
• External parasites (like ear mites)
The most severely affected patients often get stuck in a cycle of inflammation,
infection, and thickening of the tissues lining the ear canal (fibrosis), which
eventually leads to narrowing of the ear canals, ruptured eardrums, and debris
and infection within the middle ear.
Over time, scar tissue occludes the canals, preventing medications from reaching
the diseased portions of the canal. The occluded canals also prevent the natural
sloughing of the canal’s skin cells, sebum (wax), and hair, which accumulate in
both the canal and middle ear, thereby intensifying the infection.
Considering the potential long-term nature of this condition, allergic otitis is a
frustrating disease for both owners and veterinarians. But for patients, the
disease is much more critical, given that they typically suffer significant pain.
What signs are associated with allergic otitis?
Affected dogs typically experience recurrent bouts of malodorous discharge,
pain, and itchiness. But a significant subset will suffer these symptoms on a
constant basis with no relief from their profound discomfort. Some pets may even
try to bite someone who attempts to touch their ears or head.
The clinical signs of otitis depend on the severity of the inflammation but may
include:
• Shaking the head or rubbing the head and ears on the floor or furniture
• Scratching at the ears
• Discharge from the ears, which can sometimes have a foul odor
• Redness of the ear canal and earflap (the ears may also feel warm when
touched)
• Ear hematoma, evidenced by a grossly swollen earflap
• Aggression whenever the head is approached
Some dogs with severe otitis may cry or groan as they rub and scratch their ears.
Others will scratch so severely that their nails create wounds on the skin around
their face, neck, and ears. If the otitis is severe or chronic, the outer ear canal
can begin to thicken and become deformed. This thickening can make the ear
opening very narrow, so cleaning the ears becomes more difficult. Ulcerations on
the inside of the ear canal can also result from infection and self-trauma.
As mentioned above, otitis that begins in the outer ear canal can ultimately
rupture the eardrum, ending in otitis media and otitis interna. Progression of this
infection into the middle and inner ear can be associated with more severe
clinical signs, including development of a head tilt, incoordination, inability to
stand or walk, hearing loss, and severe, unrelenting pain.
A medical history and physical examination findings can provide valuable
information for your veterinarian when trying to diagnose an ear infection. The
medical history may include trying to determine how long the ear infection has
been going on, whether it has occurred before and whether any other signs of
illness have been observed. Physical examination findings may reveal evidence
of underlying illness, such as thyroid disease and Cushing’s disease.
How is allergic otitis diagnosed?
Diagnosis of otitis is usually based on a history of previous ear infections and
physical examination findings. Redness, inflammation, discharge, and other
changes within the ear will readily indicate the presence of an ear infection.
That’s the easy part. The hard part is finding out a) what kinds of microorganisms
are taking advantage of the dog’s inflamed ears and b) what’s causing the
inflammation in the first place. Determining both a) and b) generally requires
diagnostic testing. In the case of identifying microorganisms, these are the tests
most commonly used:
Microscopy: The most common test used to identify the presence of mites,
bacteria, and yeast is a simple evaluation of the discharge obtained from
the ear under a microscope. Mites are readily identified in this way. With
special staining techniques, yeast and bacteria can also be identified and
their characteristics evaluated.
Culture and sensitivity testing: Testing the debris inside a dog’s ear using
simple microscopy isn’t always enough when the otitis has been stubborn
or severe. Obtaining a sample of the discharge using a sterile swab and
submitting it to a diagnostic laboratory will help determine exactly which
bacteria and/or yeast are present. This information helps veterinarians
devise the ideal drug strategy to treat the infection.
Underlying illnesses leading to the overgrowth of microorganisms will require a
different approach. Here are the most common tests:
Otoscopy: An otoscope is a tool used to help a veterinarian visualize the ear
canal. This is the ideal tool to help identify the presence of an eardrum
rupture, a polyp, or a mass in the ear canal. Unfortunately, most dogs
require sedation — if not anesthesia — before they’ll submit to this kind of
examination.
Thyroid testing: This determines if thyroid disease may be playing a role.
Adrenal gland testing: Tests to explore the possibility of Cushing’s disease are
sometimes required in dogs with otitis externa.
Allergy testing: A blood test can help identify allergens causing the clinical
signs. Once allergens are identified, a solution is formulated so that
injections can be given at home to desensitize the pet to the allergens.
Food trial: Since food allergies are such a common feature in the chronic otitis
landscape, food trials are perhaps even more important than blood
testing. Most food allergic dogs are allergic to the primary protein source
in their food. A food trial’s goal is to change the proteins the patient eats
to those it has never been exposed to before. If the otitis resolves when
the diet is changed, a food allergy may be the underlying cause of the
condition. A 12- to 16-week period in which the diet is restricted is
considered the ideal approach to undertaking food trials.
How is allergic otitis treated?
Treatment of chronic otitis is a multistep process. First, the bacterial and fungal
(yeast) component must be addressed along with the inflammation. The following
strategies are typically used:
• Cleansing the ear canal is always recommended to clear accumulated debris. If the otitis is painful and/or an extensive process, cleansing should ideally
be undertaken with the pet under sedation or anesthesia. Otoscopy is
often recommended as an aid in this process.
• Topical medication tailored to treat the specific bacteria, yeast, or mites present is typically used (these are usually available as either ear drops or ointments). These include antibiotics, antifungals (to kill yeast), anti- inflammatory drugs (like cortisone), and topical anesthetics.
• Systemic antimicrobials (antibiotic given by mouth or injection) are indicated in some cases, such as if the eardrum is ruptured. Ideally, antibiotic therapy
is based on the results of culture and sensitivity testing.
• Systemic anti-inflammatory medications, such as corticosteroids, are
sometimes employed to reduce the pain, redness, and swelling.
Antihistamines may also be prescribed.
How do you prevent it?
The key to preventing allergic otitis is to reduce the pet’s allergies as much as
possible. The cornerstone of that plan is monthly flea control with an effective
flea control medication. Regular checks for internal parasites are important. If
parasite control does not prevent recurrence, food trials and allergy testing often
reduce or completely prevent the return of clinical signs.