Seborrhea (Dry Skin or Dandruff) in Dogs
Overview of Seborrhea (Dry Skin or Dandruff) in Dogs
Seborrhea or scaly skin is common in dogs and and is more a symptom than a disease. Some refer to seborrhea as dry skin or doggy dandruff. Seborrhea can be dry (seborrhea secca) or oily (seborrhea oleosa). Different dog shampoos are used according to the type of seborrhea present.
In most cases, the scales are secondary to another skin disease. In these cases, the scaling was not usually evident at a young age and occurred as a consequence of itching or other skin problems. Identification of the underlying cause is important to control the excessive scaling.
In some cases as in cocker spaniels, the scaling is primary and animals are born with a defect of keratinization. In these cases, the problem is evident at a young age, usually less than one year of age, and the ears are frequently affected as much as the rest of the body. Topical and systemic therapy (retinoids) may be used to normalize the turnover of the epithelial cells.
Diagnosis of Seborrhea (Dry Skin or Dandruff) in Dogs
The identification of the underlying disease responsible for seborrhea is of crucial importance. In order to do this, it is important for your veterinarian to:
- Take a complete history that includes age of onset of the skin disease, the appearance of the first sign of skin disease. Were the scales the first thing that you noted or did your animal have bumps first and then start breaking with scales? Also, was itching the first thing you noted, or did the itching come after all the skin lesions.
- Perform a complete physical examination. If a primary disease is responsible for the seborrhea, ear disease is also present.
- Do skin cytology. Swab or tape impression of the skin may provide useful information regarding the type of skin infection present. Skin infections significantly contribute to the level of itching.
- Take skin biopsies. In order to identify the underlying cause of seborrhea or to confirm a primary disease, a biopsy may be necessary.
Treatment of Seborrhea (Dry Skin or Dandruff) in Dogs
An excessive amount of oil on the skin facilitates the growth of bacteria and yeast. Most animals with seborrhea have concurrent skin infections (bacteria and yeast) and will require treatment. Your dog may need to take antibiotics or antifungal medications for several weeks to eliminate the infection.
Topical therapy is also important to remove the excessive amount of scales. Various shampoos and conditioner may be necessary.
Clipping is usually necessary in animals with long and thick hair coats. This facilitates bathing and decreases the amount of shampoo required.
Bathing is necessary at least once a week. Some dogs may need a bath with a medicated shampoo twice or three times a week. Different shampoos and conditioners are used according to the infection present and the type of seborrhea. Some are good for dry skin (Allergroom®), while others are good for greasy skin (LyTar®). Some shampoos are antibacterial (OxyDex®), while others are antifungal (Selsun Blue® animals).
A contact time of 10 to 15 minutes is crucial for the success of shampoo therapy. Leave-on conditioners may be used after the shampoo to have a prolonged effect. Products available on the market are antibacterial (Resi-Chlor®), anti-itchy (Resi-Cort®) and antifungal (Resi-zole®).
Information In-Depth on Canine Seborrhea
Most cases of seborrhea are secondary to another skin disease. To differentiate between primary and secondary seborrhea, it is important to follow a well-organized plan to rule out other diseases. An accurate diagnosis is important for appropriate therapy and prognosis.
Secondary seborrhea is by far more common than primary seborrhea and the list of differentials is very extensive since almost any disease in veterinary dermatology may have scaling and flaking as a clinical sign. Scaling secondary to another disease may be divided into two big groups: pruritic and non-pruritic.
- Pruritic causes for secondary seborrhea include: scabies, flea allergy, food allergy, atopy, Cheyletiellosis, pyoderma and Malassezia.
- Non-pruritic causes for secondary seborrhea include: demodicosis; dermatophytosis; endocrine diseases (hypothyroidism, Cushing’s, sex hormone imbalance); pemphigus foliaceous; mycosis fungoides (this disease can be very pruritic); chronic steroid administration; dietary reasons (fatty acid deficiency); and environmental factors (low humidity).
- Primary seborrhea (generalized) may be classified into: primary idiopathic seborrhea; Vitamin A responsive dermatosis; epidermal dysplasia; sebaceous adenitis; follicular dystrophy; Schnauzer comedo syndrome and ichthyosis. Differentials for localized primary keratinization disorders include: lichenoid psoriasiform dermatosis (pinnae are usually affected); Zinc responsive dermatosis; nasodigital hyperkeratosis; canine ear margin dermatosis; and canine acne.
Primary diseases of keratinization are usually manifested by excess of scale formation. They are usually genetic diseases and affected patients have a family history. Since these are hereditary conditions, the disease is usually evident at a young age, usually less than two years.
Veterinary Care In-Depth on Seborrhea
Differentiation between primary and secondary seborrhea is an important step in the approach of a case of seborrhea. This comes from the history, the distribution of the lesions and exclusion of concurrent disease.
- Cytology provides information regarding the secondary skin infections, which are present in the majority of cases at time of presentation. Swabs or tape impressions can be prepared and stained.
- Dogs should be re-evaluated for scaling and pruritus after resolution of skin infections. If scaling is not present any longer, seborrhea was secondary. At that stage the underlying cause for skin infections should be pursued. This is done by evaluating the level of pruritus (itching). If, on the other hand, scaling is still present, then it should be considered whether this is secondary to pruritus or not. If no pruritus is present then diseases like demodicosis, endocrine, autoimmune disease or diseases of keratinization are possible. A biopsy would be indicated to rule in/out diseases.
Treatment of seborrhea includes treatment of secondary skin infections and of the underlying disease of keratinization. Glucocorticoids should not be used during the time in which the diagnostic evaluation is done as they may affect the ability to control the pyoderma and they interfere with the evaluation of pruritus.
Topical Therapy for Seborrhea in Dogs
Topical therapy rarely works when used alone. However, it is a very effective adjunct therapy to get faster resolution of a skin problem. In general, bathing should be continued over at least a 10 to 15 minute period for proper hydration of the skin and to allow the active ingredients to work.
- Shampoos. Best results are obtained by shampooing frequently to control the dermatosis (skin problem) initially and then decreasing the frequency for maintenance of remission. Topical therapy is not a substitute for managing the dermatosis by establishing a definitive diagnosis as soon as possible.
- Humectants and emollients. If the seborrhea is dry, humectants and emollients are indicated. Contact time of 10 to 15 minutes should be allowed to properly hydrate the stratum corneum. If contact time is too short or if baths are given too frequently, the effect will be opposite. The application of bath oil when the skin is still wet will help to hold externally applied water to prolong hydration.
Humectants are agents that work by being incorporated in the stratum corneum and by attracting the water that is in the lower layers of the epidermis. These agents include urea, sodium lactate, lactic acid and propylene glycol and work even if applied in between baths. Lactic acid has hygroscopic activity at low concentration and keratolytic activity at higher concentrations. It has been incorporated into liposomes to ensure a slow release over time and thus a longer residual activity (Microperl Humectant Spray®).
Emollients are agents that soften the skin because they decrease transepidermal water loss. They are usually oils and work if applied after a bath. They fill the spaces between dry flakes with droplets of oil.
- Degreasers. If the seborrhea is greasy then degreasers are more appropriate. Keratolytic agents cause cell shedding while keratoplastic agents cause a normalization of the epidermal cell kinetics. Most agents used in veterinary dermatology for the treatment of seborrhea have both properties. These products have to be used quite often in order to be effective (two to three times/week).
- Clipping. A thick hair coat, like the one of a cocker spaniel, will prevent the shampoo from reaching the skin, therefore it is crucial to the success of therapy that the hair is always kept very short. This will reduce the amount of shampoo, will allow better contact with the skin surface and thus enhance efficacy.
Systemic Therapy for Seborrhea in Dogs
Most cases require systemic treatment for secondary skin infections. Antibiotics and antifungal therapy are usually used for three to four weeks.
Systemic therapy for primary diseases of keratinization includes the use of retinoids and Vitamin A derivatives. Retinoids have been tried for the management of this disorder (retinol, isotretinoin, etretinate).
These compounds have the ability to regulate the proliferation and differentiation of epithelial tissues. Isotretinoin seems to work better in cases where the disease is the hair follicle and sebaceous glands (Schnauzer comedo syndrome and sebaceous adenitis), while etretinate works better in hyper proliferative epidermal disorders (idiopathic seborrhea of cocker spaniels, English springer spaniels, Irish setters).
- Response to therapy should be seen within the first two months of therapy. Synthetic compounds have a long half-life and are stored for a long time in the body fat.
- Toxicity in animals seems to be less of a problem than in humans; however, keratoconjunctivitis secca (dry eye), increase of triglycerides, cholesterol, liver enzymes, pruritus, vomiting, diarrhea and stiffness have been reported. All these compounds are to be avoided in pregnant animals due to potential fetal malformations.