Primary seborrhea is an inherited disorder of the skin in which the outer layer of the skin (the epidermis), the sebaceous glands, and part of the hair follicles are hyperproductive. The rate of cell turnover in these tissues is significantly increased, causing excessive production of scale (dry flakes of skin) and sebum (fatty lubricating substance). Seborrhea oleosa is the more greasy form while seborrhea sicca is a dryer form. Many dogs have a combination of both types. Chronic waxy ear infections (otitis externa) also occur commonly as part of this disorder.
Signs of primary seborrhea are usually apparent by a year of age. Affected dogs are often greasy, scaly and smelly.
Secondary seborrhea is seen in older dogs. It looks the same clinically but is a response by the skin to other conditions, rather than an inherent defect in the skin itself.
Primary seborrhea is probably inherited as an autosomal recessive trait in the West Highland white terrier, and this may also be true in other breeds. This means there can be affected puppies in a litter where both parents have normal skin but carry the gene for seborrhea. Autosomal dominant inheritance with variable expressivity may be the mode of inheritance in some breeds.
Early evidence of the disorder such as mild flaking and dullness of the coat may appear as young as 10 weeks of age. Because these signs are subtle, they often go unnoticed. However, usually by a year to 18 months, the signs have become pronounced. Affected dogs commonly have a dull coat with excessive scaling, a greasy feel and smell to the skin (especially in areas of body folds), smelly waxy ears which may be infected, thickening of the foot pads, and dry brittle claws. Some breeds (West Highland white terrier, cocker spaniel, springer spaniel, Basset hound, Shar-pei) are more prone to the greasy form of seborrhea (seborrhea oleosa) with chronic ear infections and greasy skin, while others (Doberman pinscher, Irish setter) are more likely to develop the dryer form (seborrhea sicca)
Dogs with seborrhea are prone to secondary infections, either bacterial or yeast, and frequently develop skin lesions and associated itching. This condition is called seborrheic dermatitis. Scratching leads to worsening of the lesions and spread of the infection.
The signs associated with primary (inherited) and secondary (response to another condition) seborrhea are the same. Your veterinarian will take into consideration your dog's clinical signs and age (primary seborrhea is seen in young dogs), and submit a skin biopsy to a veterinary pathologist who will look for changes in the skin typical of primary seborrhea, to rule-out other conditions that cause similar clinical signs. (This is a simple procedure, done with local anaesethetic, in which your veterinarian removes a small sample of your dog's skin.)
When there is severe seborrheic dermatitis, the secondary infections must be cleared up before a diagnosis of primary seborrhea can be made.
Primary seborrhea requires life-long management. There is no cure, and the ease of control varies between dogs. Dry scaly seborrhea can usually be controlled more easily than the greasy form. You and your veterinarian will need to work together to determine what is best for your dog. You will quickly become an expert on recognizing changes in your dog's skin and ears, and knowing when veterinary care is required.
Antiseborrheic shampoos and moisturizers are the most important components of treatment. Initial bathing of 2 or 3 times per week is generally required, with frequency gradually reduced to a maintenance level as the condition is controlled. If your dog has a secondary bacterial or yeast infection (as is common), this must be treated with appropriate medication at the same time that antiseborrheic therapy is started.
Effective bathing requires that the medicated shampoo remain in contact with the skin for 10 to 15 minutes after lathering, followed by very thorough rinsing which removes debris (scales, grease) and shampoo, and also moisturizes your dog's skin. An after-bath rinse will also help to retain moisture. Occasional misting of the coat with the dilute rinse can often reduce the frequency of bathing required. Careful monitoring is required, since over-bathing can worsen seborrhea.
There are a large number of antiseborrheic products available. Your veterinarian will likely suggest a milder product to start, and change to a stronger one if necessary. Stronger products are usually required to control dogs with greasy skin, with possible switch to a milder product for maintenance. Long hair makes effective shampooing more difficult so it is best to keep the coat short.
Ear infections are common in seborrheic dogs. The best way to keep on top of these is to check your dog's ears regularly. Your veterinarian will show you how to flush your dog's ears with a product designed to reduce wax build-up. Use this when your dog's ears have a waxy odour. Signs of an infection include a need to clean the ears more frequently, itchiness (as shown by head shaking, pawing at the ears, rubbing the head along the carpet) and/or an unpleasant odour. This requires prompt treatment, usually for 2 to 3 weeks.
It is important to watch carefully for any other conditions in your dog, as the signs of seborrhea will worsen dramatically if s/he develops nutritional inadequacies, external parasites (fleas for example) or some other illnesses. A sudden worsening of seborrhea (a need for more frequent bathing or an increase in odour) can also indicate a secondary skin infection to which these dogs are prone. Such infections should be brought under control quickly with the appropriate medication, as they can quickly become severe and widespread.
In some dogs it is almost impossible to control the seborrhea and recurring yeast or bacterial infections, despite the most diligent efforts of their owners. Various drugs have been tried in these dogs with varying results. If effective, they are needed life-long and all have side effects, so they are used only where other measures fail.
For the veterinarian: There has been some success in the treatment of cocker spaniels with the retinoic acid etretinate. Corticosteroids and cytotoxic drugs like methotrexate are used with some success as well, but the long term use required is associated with potentially severe side effects.
Staphylococci and Malassezia are opportunistic pathogens that are believed to play a significant role in seborrheic dermatitis and otitis. Intense pruritis is common where there is secondary infection with these organisms.
Besides primary seborrhea, rule-outs in young dogs (less than 12 to 18 months) with seborrheic signs include demodicosis, cheyletiellosis, food hypersensitivity, epidermal dysplasia, nutritional deficiency, and ichthyosis.
Dogs with primary seborrhea and their close relatives (parents and siblings) should not be used for breeding.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Campbell, K.L. 1997. Diagnosis and management of keratinization disorders in dogs. ACVIM - Proceedings of the 15th Annual Vet. Medical Forum. pp 220-222.
Power, H.T., Ihrke, P.J. 1995. The use of synthetic retinoids in veterinary medicine. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p585-590. W.B. Saunders Co., Toronto.
Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Muller and Kirk's Small Animal Dermatology. pp 737-743 W.B. Saunders Co., Toronto. This has a practical and detailed section on clinical management.