Seborrhoea

KERATINISATION DEFECTS (SEBORRHOEA)

Seborrhoea literally is defined as ‘flow of sebum. Sebum is the natural skin secretions and consists of various lipids, waxes, proteins etc. In veterinary, and human dermatology, seborrhoea is used to describe a number of skin conditions that are associated with excessive production of scale (keratinisation defect) together with either excessive or deficient sebum production.

Classification.

Three types of seborrhoea are described:

Seborrhoea oleosa (greasy)
Seborrhoeic sicca (dry)
Seborrhoeic dermatitis (inflamed)

These terms are useful when discussing seborrhoea but in practice one may see combinations of the various types in any one case.

Seborrhoea oleosa.

Waxy or greasy deposits build up on the skin and hair coat usually with excessive scale. Plugs of waxy material often adhere to hairs and may resemble louse eggs. A rancid smell due to decomposing fats often accompanies this type of seborrhoea. Classically this is seen in Spaniels.

Seborrhoea sicca.

Here the skin and hair coat is dry and again excessive scale is found. The Doberman is prone to this type of seborrhoea.

Seborrhoeic dermatitis.

This may be either localised or generalised. Patches of crust and scale are seen. The skin underneath these lesions is inflamed and often weeping.

In all types of seborrhoea because of the abnormal changes present at the skin surface, there is a tendency for pathogenic bacteria to predominate on the skin of dogs suffering from seborrhoea. Pyodermas are therefore commonly seen in dogs suffering from seborrhoea.

The Spaniel, Dobermann, Irish setter, German Shepherd dog and West Highland terrier are breeds that are prone to develop seborrhoea.

A large number of skin diseases may potentially result in the development of a seborrhoeic skin disorder and it is essential to investigate each case thoroughly to determine if a specific cause can be found and so apply appropriate treatment. Possible causes of seborrhoea are:

Parasitic: Fleas, Lice, Sarcoptic Mange, Cheyletiella.

Infectious: Bacteria or fungi.

Hormonal: Hypothyroidism or Cushing’s disease among others.

Diet related: Fat, Vitamin A, or Zinc responsive.

Allergy: Atopy, Fleas, Food allergies.

Systemic Illness: Liver or intestinal disease

Neoplasia: Skin lymphoma

Primary (Idiopathic) Seborrhoea

Here the cause is not known. Before a diagnosis of primary seborrhoea is made all possible causes of seborrhoea should be investigated and excluded. Certain breeds appear to have a high incidence of primary seborrhoea (see seborrhoeic breeds above) and familial factors may play a part.

The spaniels (Cocker, Springer and English) are all prone to primary seborrhoea. Typically this starts in early adult life (3-5 years of age) and persists for the remainder of the dog*s life. The normal epidermal cell turnover time is about 21 days but dog*s suffering from primary seborrhoea have been shown to have epidermal cell turn over times as short as 3 days. Itching is variable but in most cases is mild to moderate.

Treatment of Seborrhoea.

If a cause for the seborrhoea can be found then this should be treated. In primary seborrhoea symptomatic treatment is all that can be offered. In general the mainstay of treatment is shampooing on a regular basis.

Antibiotic treatment may be required where pyoderma is present.

Shampoos: These are usually the main means of control. A variety of shampoos are available and it is usually worthwhile advising the owner to try several to see which suits best. Useful shampoos include - coal tar based (Polytar), antibacterial (Oxydex), scale control (Seleen) or normal (Hexocil). If no shampoo is better then another the cheapest can be used. Shampooing should be carried out to the manufacturers instructions. This usually requires shampooing and waiting for 5-10 minutes so that the active ingredients can work. Initially frequent shampooing is advised - once a week. Once under control then the time interval between shampooing can be increased but shampooing should be continued on a regular basis.

Emollients: These are used to hydrate the skin and reduce scale. They are of most use in dry seborrhoea problems.

Diet: Supplementation with essential fatty acids can be very useful but may be expensive. Evening primrose oil nearly always improves coat and skin condition. 500 -l000mg/ 10kg body weight is a sufficient dosage. Supplementation should be continued for at least 9-12 weeks before it is considered not to be of use. Some dogs improve on a low protein diet or an animal protein free (soya based) diet. If a dietary change is made it should be made gradually and used over a period of 9-12 weeks before a decision is made as to its usefulness or not.

Tail gland hyperplasia.

In the dog at the dorsal tail head there is an oval area of skin which is very rich in sebaceous glands. In some dogs the glands become hypertrophied and the skin becomes thickened and bald. Clinically a circumscribed round to oval area of alopecia is seen with some scale and thickening of the skin. Occasionally secondary bacterial infection occurs.

The cause is unknown but in some cases is associated with hypothyroidism (more generalised skin problems will also be seen) and some types of testicular tumours.

No treatment is usually necessary unless secondary infection is present in which case antibiotics can be given. Topical cleansing to remove scale and debris can be advised but regrowth of hair is very unlikely.