Otitis Externa in Dogs: Causes, Symptoms, and Treatment
Otitis Externa in Dogs: Causes, Symptoms, and Treatment
What is otitis externa in dogs?
Otitis externa is an inflammation of the external auditory canal (meatus acusticus externus) in dogs—one of the most common conditions seen in small animal practice. The ear canal is lined with epithelial tissue containing ceruminous glands and hair follicles; when the microenvironment is disrupted, bacteria (primarily Staphylococcus pseudintermedius and Pseudomonas aeruginosa) and yeasts (Malassezia pachydermatis) proliferate, triggering inflammatory reactions characterized by pain, itching, and discharge.
Otitis externa is almost never a primary condition, but rather a symptom of an underlying disease—often atopic dermatitis or food hypersensitivity. Treating only the ear without identifying the cause is like going in circles.
Background + Scientific Context
Gotthelf (2004, *Small Animal Ear Diseases*) describes the PSPP concept of otitis externa: primary factors(allergies, endocrinopathies, foreign bodies), S(bacteria, yeasts), predisposingfactors (anatomy: floppy ears, ear canal stenosis), and perpetuatingfactors (chronic changes: hyperplasia, fibrosis). Without addressing the primary factors, recurrences are inevitable. Otoscopy is mandatory before any treatment—a perforated eardrum fundamentally changes the choice of medication.
Angus (2004, VCNA, PubMed 14733977) describes the importance of ear cytology: examining an ear swab under a microscope is quick, inexpensive, and clinically crucial—distinguishing between bacterial otitis (cocci vs. rods) and yeast otitis (Malassezia) determines the choice of topical ear medication. Pseudomonas otitis (Gram-negative rods) requires different antibiotics than staphylococcal otitis; a cytological misdiagnosis leads to treatment failure.
Nuttall and Cole (2007, Veterinary Dermatology, PubMed 17941887) conducted a systematic review of interventions for Pseudomonas otitis: Pseudomonas aeruginosa is the most clinically challenging pathogen—often multidrug-resistant and resistant to treatment if managed inadequately. Ear cultures with an antibiogram are mandatory when Pseudomonas is suspected. Topical silver sulfadiazine or fluoroquinolone preparations are the treatments of choice; systemic antibiotics are indicated for deep involvement.
Vitomalia-Position
Otitis externa is too often treated as a localized ear problem—without cytology, without investigating the underlying condition, and without examining the eardrum. This leads to recurrences, the development of resistance, and chronic otitis with irreversible damage. Every ear infection deserves a thorough evaluation, not self-treatment with over-the-counter ear drops.
When does otitis externa become a concern?
- Scratching the ear, shaking the head, tilting the head — early warning signs
- Odor or discharge from the ear
- Dogs with floppy ears, atopic conditions, or a history of allergies
- Recurrent ear infections despite treatment
- Pain when touching the ear — possible involvement of the middle ear
Practical application
Pathogen profile and initial treatment steps:
| Cytology results | Likely pathogen | Topic of Choice |
|---|---|---|
| Grapes (cluster) | Staphylococcus | Fusidic acid, gentamicin |
| Chopsticks (large, blue) | Pseudomonas | Fluoroquinolone, silver sulfadiazine |
| Yeast (peanut-shaped) | Malassezia | Clotrimazole, Miconazole |
| Mixed Flora | Combined infestation | Broad-spectrum combination medication |
Diagnostic Checklist: 1. Otoscopy: Is the eardrum intact? Are there any foreign objects? Is there hyperplasia? 2. Cytology: Ear swab prior to treatment, Gram stain, or Diff-Quik 3. In case of recurrence: Culture + antibiotic susceptibility testing 4. Investigate underlying conditions: allergy history, thyroid function, sex hormones
Cleaning before taking medication: - Zeruminolytic cleanser before topical application — otherwise, no contact with the active ingredient - In cases of a perforated eardrum: use only aqueous solutions; do not use alcohol or propylene glycol
Common Mistakes & Myths
- “I’ll treat the ear myself—it’s just an infection, after all.” Without a cytology test, antibiotics are prescribed blindly; a yeast-induced otitis will be made worse by antibiotic ear drops. A visit to the vet and a cytology test are not optional.
- “The ear infection is gone—that’s it.” Without treating the underlying condition (atopy, food hypersensitivity), the next recurrence will follow within a few months. True healing requires treating the root cause.
- “Administer ear drops after swimming as a precaution.” Prophylactic antibiotic ear drops promote the development of resistance. Dry the ear canal after swimming—do not use antibiotics unless medically indicated.
Current State of Research (2026)
Otitis externa affects an estimated 10–20% of all dogs in small animal practice and is the most common reason for referral in veterinary dermatology. Atopic dermatitis is identified as the primary factor in >50% of recurrent otitis cases. Multidrug-resistant Pseudomonas strains are a growing clinical problem; the development of resistance due to inadequate treatment and the use of over-the-counter antibiotics is viewed critically. PSPP diagnostics are considered the gold standard.
Frequently Asked Questions
How can I tell if my dog has an ear infection?
Common signs: Scratching the ear, frequent head shaking, tilting the head, odor coming from the ear, redness or swelling of the outer ear, yellowish-brown or pus-like discharge, and pain when the ear is touched. If these symptoms are present, see a veterinarian; do not attempt to treat the condition yourself.
Why do ear infections keep coming back?
Recurrent otitis is almost always a sign of an untreated underlying condition—often atopy, food hypersensitivity, or hypothyroidism. Ear drops only treat the secondary infection, not the underlying cause. A long-term solution requires allergy testing and treatment of the underlying condition.
Can I give my dog over-the-counter ear drops?
Without a cytology test, there is a high risk of treating the wrong pathogen—or of making a yeast-induced ear infection worse with antibiotics. If the eardrum is perforated, certain ingredients can damage the inner ear. Ear infections should always be evaluated by a veterinarian before any medication is administered.
Related terms
Sources & Further Reading
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Gotthelf, L. N. (Ed.). (2004). Small Animal Ear Diseases: An Illustrated Guide (2nd ed.). Elsevier. ISBN 9780721600673.
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Angus, J. C. (2004). Otic cytology in health and disease. Veterinary Clinics of North America: Small Animal Practice, 34(2), 411–424. https://pubmed.ncbi.nlm.nih.gov/14733977/
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Nuttall, T., & Cole, L. K. (2007). Evidence-based veterinary dermatology: a systematic review of interventions for treatment of Pseudomonas otitis in dogs. Veterinary Dermatology, 18(2), 69–77. https://pubmed.ncbi.nlm.nih.gov/17941887/