In dogs, seborrhea is a skin disease that is characterized by a defect in keratinization or cornification of the outer layer of the skin, hair follicles, or claws. Keratinization is the process in which the protective outer layer of skin is being constantly renewed by new skin cells. Seborrhea results in increased scale formation, occasionally excessive greasiness of the skin and hair coat, and often secondary inflammation and infection.
Primary seborrhea is an inherited skin disorder. It is seen most frequently in American Cocker Spaniels, English Springer Spaniels, Basset Hounds, West Highland White Terriers, Dachshunds, Labrador and Golden Retrievers, and German Shepherd dogs. Among dogs with seborrhea, there is usually a family history of the disorder, suggesting genetic factors are involved. The disease begins at a young age (usually less than 18 to 24 months) and progresses throughout the dog’s life.
Secondary seborrhea is a sign of an underlying disease that causes excessive scaling, crusting, or oiliness, often accompanied by pus-filled inflammation, infection, and hair loss.
Signs and Diagnosis
A diagnosis of primary seborrhea is reserved for dogs in which all possible underlying causes of seborrhea have been excluded. Most dogs with seborrhea have the secondary form of the disease. The most common underlying causes are hormonal disorders and allergies. The goal is to identify and treat these underlying causes. Allergies are more likely to be the underlying cause if the age of onset is less than 5 years. Hormonal disorders are more likely if the seborrhea begins in middle aged or older dogs. A lack of itching helps to exclude allergies, scabies, and other itching diseases. If itching is minimal, your veterinarian will seek to exclude hormonal disorders, other internal diseases, or other primary skin diseases. If itching is significant, allergies, scabies, and fleas will also be considered by your veterinarian.
Other important considerations in making a diagnosis include the presence of excessive urination, excessive drinking, heat-seeking behavior, abnormal estrous cycles, skin infections, the season, diet, response to previous medications, fungi or bacteria present, and the environment.
Your veterinarian will give your pet a thorough physical examination, including internal organ systems and a comprehensive skin examination. This is the first step in identifying the underlying cause. The skin examination documents the type and distribution of the abnormalities; the presence of hair loss; and the degree of odor, scale, oiliness, and texture of the skin and hair coat. The presence of follicular boils, papules (pimples), crusts, and other bumps usually indicates the existence of a superficial pyoderma (bacterial infection). Darkening indicates a chronic skin irritation (such as infection or inflammation), and skin thickening indicates chronic itching. Yeast infection will always be considered during this process.
Secondary infection is a problem for dogs with seborrhea. The keratinization abnormalities in seborrheic dogs usually provide ideal conditions for bacterial and yeast infections. The self-trauma that occurs in itchy animals increases the likelihood of a secondary infection. The infections add to the itchiness and are usually responsible for a significant amount of the inflammation, papules, crusts, hair loss, and scales. Samples of the affected areas are taken to identify the quantity and type of bacteria or yeast present. In a seborrheic dog with itching, the infection may cause all or most of the signs. Other diseases may be uncovered by clearing the infections. Thus, you should be sure to comply with any follow up examination requests made by your veterinarian.
Additional tests may also be necessary, including skin scraping, fungal and bacterial cultures, flea combing, skin biopsy, and blood and urine tests.
Treatment is needed to keep your dog comfortable while the underlying cause is identified and secondary skin diseases are corrected. In addition to treating any secondary infections with antibiotics, medicated shampoos are often used to help control the seborrhea and speed the return of the skin to a normal state. Medicated shampoos can decrease the number of bacteria and yeast on the skin surface, the amount of scale and sebum present, and the level of itching. They may also help normalize skin cell replacement.
Most products contained in medicated shampoos can be classified based on their effects. Keratolytic products include sulfur, salicylic acid, tar, selenium sulfide, propylene glycol, fatty acids, and benzoyl peroxide. They remove excess dead skin cells. This reduces the scale and makes the skin feel softer. Shampoos containing keratolytic products frequently increase scaling during the first 14 days of treatment, due to the loosened scales getting caught in the hair coat. The scales will be removed by continued bathing. Keratoplastic products help normalize keratinization and reduce scale formation. Tar, sulfur, salicylic acid, and selenium sulfide are examples of keratoplastic agents. Emollients (lactic acid, sodium lactate, lanolin, and numerous oils, such as corn, coconut, peanut, and cottonseed) reduce water loss from the skin. They work best after the skin has been rehydrated and are excellent products after shampooing. Antibacterial agents include benzoyl peroxide, chlorhexidine, iodine, ethyl lactate, tris-EDTA, and triclosan. Antifungal ingredients include chlorhexidine, sulfur, iodine, ketoconazole, and miconazole. Boric and acetic acids are also used as topical antibiotics. Most medicated shampoos are a combination of these ingredients.
Follow the advice of your veterinarian regarding the most appropriate medicated shampoo for your pet with seborrhea. The selection of a medicated shampoo is based on hair coat and skin scaling and oiliness. Never use a shampoo formulated for people without the consent of your veterinarian.
Antibiotics are typically recommended for 3 to 4 weeks for bacterial skin infections. Fungal infections are common and are treated with antifungal medications.