Allergic Otitis Externa in Dogs and Cats: Diagnosis and Management

Allergic otitis externa (AOE) is a frequent manifestation of allergy in companion animals and, in some cases, may be the only clinical sign. It is an inflammatory condition of the ear and should not be confused with primary infection, which often occurs secondarily. While managing secondary infections is important, identifying and addressing the underlying cause of otitis externa is critical to preventing recurrence. According to the 2023 AAHA Management of Allergic Skin Diseases in Dogs and Cats Guidelines¹: 

• Over half of dogs and around 20% of cats with allergies develop AOE. 

• Other primary causes—including parasites, foreign bodies, neoplasia, endocrinopathy, and keratinization disorders—should always be ruled out. 

• AOE is frequently associated with atopic dermatitis and food allergy, but not with flea allergy dermatitis. 

Clinical Presentation 

AOE typically presents as bilateral ear disease, though severity may differ between ears. Key clinical features include: 

• Otic pruritus: head shaking, scratching at ears, rubbing face/head 

• Pain and erythema 

• Ceruminous (waxy) exudate 

• Periauricular alopecia and excoriation 

Secondary infection may add: 

• Malodorous exudate 

• Crusting, scaling, and erosions 

• Asymmetric ear carriage 

Red flags suggesting otitis media/interna: 

• Hearing loss 

• Head tilt or vestibular disturbances 

• Horner’s syndrome 

• Temporomandibular joint pain 

Diagnosis 

A thorough ear evaluation is crucial in patients with dermatologic disease, including: 

• Examination of pinna and periauricular region 

• Palpation of ear canals 

• Otoscopy for deeper structures and to rule out other primary causes 

Chronic inflammation can cause: 

• Altered pliability of ear cartilage, sometimes leading to calcification 

• Ceruminous gland hyperplasia → cobblestone-like appearance 

• Stenosis of ear canals due to edema, inflammation, or chronic pathologic changes 

Secondary infection considerations: 

• Dysbiosis is common in dogs with atopic dermatitis; Staphylococcus spp. may predominate 

• Yeast overgrowth (Malassezia spp.) is often secondary to inflammatory changes 

• Ear cytology is essential in every case: 

• Stained dry mount: assesses bacteria and yeast 

• Unstained mineral oil wet mount: rules out ectoparasites (important in cats due to Otodectes) 

• Training technicians in cytology improves clinic efficiency 

Treatment 

Topical therapy should be guided by cytologic findings. Key points: 

• In cases of abundant exudate, perform in-clinic ear flush 

• Be cautious with ruptured tympanic membranes—select safe antimicrobials and cleaning agents 

• Referral to a board-certified dermatologist is recommended if: 

• Multiple treatment protocols fail 

• Disease persists beyond 3–6 months 

• Chronic infection complicates management 

Short-Term Management 

Goals: reduce inflammation and treat secondary infections. Options include: 

• Oral corticosteroids (short tapering course) 

• Oclacitinib 

• Topical corticosteroids for inflammation control 

Long-Term Management 

Goals: maintain ear health and manage underlying allergy. Strategies include: 

• Routine topical maintenance therapy: ear cleansing based on patient needs 

• Use of cleansing agents that promote epidermal barrier function and reduce microbial adherence 

• Topical glucocorticoids (e.g., hydrocortisone, dexamethasone) to prevent flares and secondary infection 

• Monitoring individual response to medications used for atopic dermatitis, as efficacy may vary 

Referral indications: 

• Complicated or resistant AOE 

• Secondary infections unresponsive to empiric therapy 

• Middle ear involvement 

Owner compliance and follow-up: 

• Demonstrate ear cleaning and topical medication application—responsibility of trained technicians 

• Interim follow-up via phone, video, or email can improve adherence and outcomes 

Conclusion 

Allergic otitis externa is a common, often bilateral, manifestation of allergy in dogs and cats that requires careful differentiation from primary infection. Early diagnosis through thorough examination and cytology, combined with targeted topical and systemic therapy, is essential. Long-term management focuses on controlling the underlying allergy, maintaining ear health, and preventing recurrence. Owner education and technician-led follow-up significantly improve treatment success, while referral to a specialist is warranted in complicated or refractory cases. 

Reference 

1. Miller J, Simpson A, Bloom P, Diesel A, Friedeck A, Paterson T, Wisecup M, Yu CM. 2023 AAHA management of allergic skin diseases in dogs and cats guidelines. Journal of the American Animal Hospital Association. 2023 Nov 1;59(6):255-84. https://www.aaha.org/wp-content/uploads/globalassets/02-guidelines/2023-aaha-management-of-allergic-skin-diseases-in-dogs-and-cats-guidelines/resources/2023-aaha-management-of-allergic-skin-diseases-guidelines.pdf.