Ear margin seborrhea is a keratinization disorder affecting the pinnal margins in dogs. Most cases are mild and result in greasy or waxy scale surrounding easily epilated hairs. Diagnosis is often presumptive and is based on clinical signs, physical examination, and exclusion of ectoparasites and secondary infection; however, skin biopsy can confirm the diagnosis and exclude other causes of pinnal margin scale and crusting. Treatment depends on disease severity and can include benign neglect or topical antiseborrheic products, such as selenium sulfide or benzoyl peroxide.
Ear margin seborrhea is a keratinization disorder that is common in Dachshunds; however, other dog breeds with pendulous pinnae can be affected. The cause of ear margin seborrhea is unknown.
Clinical Findings of Ear Margin Seborrhea in Dogs
Lesions of ear margin seborrhea usually affect the apex of the pinna on both sides but can progress to involve the whole ear margin. Lesions appear as waxy, gray-to-yellow scales adherent to the base of hair shafts (follicular casts). Plugs of hair are easily epilated, leaving behind a shiny surface to the skin. In severe cases, the ear margins are edematous and fissured (see ).
Ear margin seborrhea in a Dachshund. Tightly adhered crust on the ear margin forms small fissures.
Courtesy of Dr. Sheila Torres.
Diagnosis of Ear Margin Seborrhea in Dogs
Diagnosis of ear margin seborrhea in dogs is based on the following:
physical examination findings
cytological evaluation to exclude bacterial and/or yeast infection
superficial and deep skin scrapings or trichograms to rule out mites, including Sarcoptes scabiei and Demodex canis
possibly, dermatophyte culture or PCR assay to rule out dermatophytosis
Skin biopsy using either a shave biopsy or wedge biopsy technique can provide a definitive diagnosis.
Histopathological findings include severe hyperkeratosis and follicular keratosis with dilated follicles filled with keratin debris.
Differential diagnoses of ear margin seborrhea include the following:
Dermatophytosis, in particular, can cause a scaling pinnal dermatitis in dogs, cats, and horses; however, the ear margin typically is not involved, and other areas of the body are generally affected as well.
Treatment of Ear Margin Seborrhea in Dogs
Treatment of ear margin seborrhea in dogs includes the use of antiseborrheic shampoos (eg, sulfur, salicylic acid, benzoyl peroxide), keratolytic products (eg, salicylic acid gel), or topical moisturizers, as needed.
Systemic medications that might help normalize the abnormal keratinization process include vitamin A (1) and essential fatty acids (2).
If severe inflammation and fissures develop, topical steroids (every 24 hours for 7–10 days) or oral glucocorticoids such as prednisone (1 mg/kg PO, every 24 hours until clinical resolution and then tapered) and pentoxifylline (10–15 mg/kg, PO, every 8–12 hours until clinical resolution and then tapered) can be beneficial (3, 4).
Key Points
Ear margin seborrhea involves idiopathic keratinization of the pinnal margin of dogs, most often in breeds with pendulous ears.
Diagnosis is usually presumptive and is based on physical examination and the exclusion of other disorders that cause pinnal margin scaling and follicular casts, especially when other areas of the body are affected.
Treatment includes the use of topical therapies, such as sulfur-based products, salicylic acid, and benzoyl peroxide, to improve epithelial turnover.
For More Information
Also see pet owner content regarding seborrhea of the outer ear in dogs.
References
Marchegiani A, Fruganti A, Spaterna A, et al. Impact of nutritional supplementation on canine dermatological disorders. Vet Sci. 2020;7(2):38. doi:10.3390/vetsci7020038
Campbell KL, Uhland CF, Dorn GP. Effects of oral sunflower oil on serum and cutaneous fatty acid concentration profiles in seborrheic dogs. Vet Dermatol. 1992;3(1):29-35. doi:10.1111/j.1365-3164.1992.tb00140.x
Miller WH, Griffin CE, Campbell KL. Keratinization disorders. In: Mueller and Kirk's Small Animal Dermatology. 7th ed. Saunders; 2012:642.
Frank LA. Cornification disorders. Paper presented at: Pacific Veterinary Conference; June 29, 2018; San Francisco, California.
