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3.10 Canine Ear Margin Dermatosis

  1. General Considerations

    1. Canine ear margin dermatosis is an uncommon idiopathic keratinization defect of the pinna margin.
    2. Lesions are usually bilateral.
    3. The cause is unknown.
    4. Dachshunds appear to be predisposed; however, other breeds can also develop this disease.

Important Facts

  • Ear margin dermatosis is an uncommon idiopathic keratinization defect of the pinna margin.
  • Lesions are usually bilateral.
  • The cause is unknown.
  • It can occur in any breed but Dachshunds appear to be predisposed.

  1. Clinical Signs

    1. Kerato-sebaceous material is tightly adhered to the skin surface and especially hair shafts of the concave and convex margins of both pinna forming what is called follicular casts.
Mild case of ear margin seborrhea. Notice a focal area with fine greasy scales (i.e. kerato-sebaceous scales) adhered to the skin surface. Greasy scales are also casting groups of hair shafts at the ear tip. Hairs epilate very easily at affected sites.
    1. Hairs epilate very easily on affected areas and alopecia may develop with time.
Moderate case of ear margin seborrhea characterized by accumulations of greasy scales along both sides of the pinna margin. Alopecia is present and scales are casting the few hair shafts still present.
Severe case of ear margin seborrhea characterized by thick layers of greasy scales protruding at various areas along both sides of the pinna margin. Alopecia is present and scales are casting the few hair shafts still present.
    1. In severe chronic cases, progression to the development of fissures may occur. Pain is typically present in these cases and fissures often bleed when the animal shakes its head.
    2. Pruritus is typically absent.

Important Points

  • Lesions are characterized by the presence of greasy scales that are tightly adhered to the skin surface and hair shafts of both sides of the margin of the pinna.
  • Lesions are typically bilateral.
  • In severe cases, the greasy scales form thick layers that affect the whole pinna margin.
  • Alopecia and fissures will eventually develop in severe cases.
  • Pruritus is usually absent.

  1. Differential diagnoses

    1. If severe pruritus is present, sarcoptic mange should be suspected and multiple skin scrapings and a treatment trial should be performed if scrapings are negative.
    2. If erythema, crusts, and/or deep erosions to ulcerations are present, vasculitis must be considered.
      1. Causes of pinna vasculitis include facial or generalized discoid lupus erythematosus, cold agglutinin disease, frostbite, and idiopathic pinna vasculitis.

  2. Diagnosis

    1. The diagnosis of early ear margin dermatosis is based on the patient’s history and presence of the characteristic ear margin lesions.
    2. Multiple skin scrapings should be performed in cases of moderate to severe pruritus to rule in scabies. If scrapings are negative, perform a parasiticidal trial to rule out scabies.
    3. A skin biopsy is the most important diagnostic procedure to differentiate the various diseases associated with pinnal vasculitis.
      1. Additional tests including CBC, chemistry profile, antinuclear antibody (ANA), and Coomb’s  should be selected based on the patient’s history and clinical signs.

Important Facts

  • The diagnosis of early ear margin dermatosis is based on the patient’s history and clinical signs.
  • If pruritus is present, perform multiple skin scrapings to rule in scabies. If scrapings are negative, perform a parasiticidal trial before ruling out scabies.
  • If erythema, deep erosions to ulcerations, and/or crusts are present, vasculitis must be considered.
  • A skin biopsy should be performed to differentiate the various causes of pinna vasculitis.
  • Selection of additional tests should be based on the patient’s history and clinical signs.

  1. Treatment

    1.  Ear margin dermatosis is typically not curable but it is a controllable disease.
    2. Mild forms are usually controlled with topical therapy.
      1. Topical treatment with antiseborrheic agents (e.g. benzoyl peroxide, tar, sulfur, salicylic acid) will remove the greasy scales (i.e. kerato-sebaceous material)
      2. The frequency of therapy varies from daily to weekly and should be tailored to each case.
    3. Topical glucocorticoid creams and/or systemic prednisone (1.1 mg/kg per day) may be indicated to reduce inflammation in severe cases.
      1. Keep in mind that idiopathic ear margin seborrhea is not associate with clinical inflammation thus, be suspicious of an underlying vasculitis if inflammation is present.
    4. Pentoxifylline can be tried at the dose of 15-20 mg/kg q 8hrs for 4 to 8 weeks. It has excellent safety margins, improves local oxygenation and has anti-inflammatory properties.
    5. Surgical removal of affected tissues can be discussed with pet owners in cases refractory to therapy.
      1. The full list of differential diagnoses should be evaluated before considering such an aggressive therapy.
      2. Educate the pet owner that lesions may return since we are not treating the cause, which is unknown.
      3. To reduce the recurrence risk, the tissue should be removed well into the normal portion of the pinnae.
      4. The surgical procedure will not be effective if the disease is due to an autoimmune disease or vasculitis.
    6. Affected dogs should not sleep close to forced-air heating ducts, wood stoves, or other dry heat sources as these may exacerbate the condition.

Important Facts

  • Ear margin dermatosis cannot be cured and treatment is symptomatic.
  • Topical treatment with antiseborrheic agents (e.g. benzoyl peroxide, tar, sulfur, salicylic acid), applied daily to weekly is the mainstay therapy.
  • Idiopathic ear margin seborrhea is not associated with clinical inflammation thus, be suspicious of an underlying vasculitis if inflammation is present.
  • Pentoxifylline (Trental®) can be tried at the dose of 15-20 mg/kg q 8hrs for 4 to 8 weeks since it is safe, improves blood oxygenation, and has an anti-inflammatory effect.
  • Surgical removal of affected tissues can be discussed with pet owners in cases refractory to therapy.
  • The full list of differential diagnosis should be considered before instituting such an aggressive therapy.
  • The procedure will not be effective if the disease is due to autoimmune disease or vasculitis.
  • To reduce the recurrence risk, the tissue should be removed well into the normal portion of the pinnae.
  • Affected dogs should not sleep by forced-air heating ducts, wood stoves, or other dry heat sources as these may exacerbate the condition.

References

Kwochka KW: Primary Keratinization Disorders of Dogs.  In: Griffin CE, Kwochka KW, MacDonald JM (eds).  Current Veterinary Dermatology.  St Louis, Mosby Year Book, 1993; p 176-190.

Kwochka KW: Overview of normal keratinization and cutaneous scaling disorders of dogs.  In: Griffin CE, Kwochka KW, MacDonald JM (eds).  Current Veterinary Dermatology.  St Louis, Mosby Year Book, 1993; p 167-175.

Miller, Griffin and Campbell.  Chapter 14. Keratinization defects. In: Muller & Kirk’s Small Animal Dermatology. 7th ed., W.B. Saunders, Missouri, 2013; p 630-646.

Power HT, Ihrke PJ.  Synthetic retinoids in veterinary dermatology.  Vet Clin North Am: Small Anim Pract, Philadelphia, WB Saunders, 1990; p 1525.

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Small and Large Animal Dermatology Handbook, Vol. 2 Copyright © 2025 by Sheila M.F. Torres, DVM, MS, PhD, DACVD is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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