Seborrhoea is often divided into primary or secondary. Primary seborrhoea is only diagnosed after all the other causes of seborrhoea have been ruled out (see below). Springer and cocker spaniels are the breeds in which primary seborrhoea has been suspected, but a thorough work up may have not been done in those reported cases to rule out underlying causes and concurrent infections. Therefore it is very likely that primary seborrhoea does not exist at all in dogs.
It is very common that dogs with an ectoparasite infestation (e.g. scabies, demodicosis), endocrine disorder (e.g. sex hormone abnormalities) or allergy (e.g. atopic dermatitis, cutaneous adverse food reaction or flea bite hypersensitivity) will also develop greasy skin.
The skin is initially erythematous, often with the presence of primary lesions like papules or pustules (concurrent bacterial infection) and with time becomes hyper-pigmented, thickened and may be covered by yellowish waxy scales (concurrent Malassezia infection). These infections will further contribute to the excessive sebum production.
The affected dogs may be very pruritic, initially lesions may be limited to the ventral areas of the neck, axillae (fig 1) and groin (fig 2), but may involve any other part of the body (fig 3). A typical rancid smell often accompanies this clinical presentation. Diagnosis is achieved with clinical and cytological examination of the skin.
The approach to cases of seborrhoea has two phases:
The fundamental properties required for a good anti-seborrhoeic shampoo are degreasing, keratoplastic and keratolytic. The most common ingredients of these shampoos are:
A recent study has shown that a shampoo containing salicylic acid, colloidal sulphur and other ingredients (chlorhexidine digluconate, coconut diethanolamide, ethoxylated lanolin and zinc gluconate) is effective and well tolerated in dogs with keratoseborrhoeic disorders (Ghibaudo, 2010). The author reports that the antimicrobial and antifungal activity of this shampoo, based on cytology performed before and after the study, was very effective and this is likely due to the synergistic effect of the sulphur & salicylic acid as well as the chlorhexidine digluconate. Chlorhexidine digluconate has a broad spectrum antibacterial activity (Lloyd, 1999) and has been shown to have superior antibacterial activity to benzoyl peroxide and ethyl lactate. It is not irritant, non toxic and has a residual action on the skin. Furthermore the author reports that the shampoo was not irritant, most likely due to the presence of zinc gluconate and lanolin, which have anti-inflammatory, soothing and softening properties (Dreno 2001).
In this study, besides the cytological (e.g. bacteria, yeasts) parameters, the clinical (e.g. erythema, pruritus) parameters were also positively changed within 2-4 weeks of shampoo therapy (Ghibaudo, 2010). Furthermore, (unpublished) studies also demonstrate that the same ingredients of the shampoo have excellent in vitro activity against Malassezia spp. and Staphylococcus spp.
The frequency of the shampoo therapy will depend on the severity of the lesions. Normally it is performed every 2-3 days at the beginning and then the interval between them increased, keeping in mind that it may take several weeks/months to restore skin normality while the underlying cause is identified/controlled. It is commonly recommended to allow a contact time of 5-15 minutes, depending on the shampoo being used.
It is not uncommon that dogs with seborrhoea are treated by alternating between shampoos with an anti-seborrhoeic and an antibacterial/anti-yeast activity, and with systemic antibiotics. It would be important to carefully evaluate the affected patient because with many of them, the overgrowth of the bacteria/yeasts would not require a systemic therapy and an antiseptic shampoo could be enough. Assuming the owners are willing to shampoo their dog, have a suitable place to do it and the patient cooperates, dispensing just one product like a medicated shampoo may increase client compliance and reduce the abuse of antibiotics, thus reducing the risk of bacterial resistance.
Fig 1 - Alopecia with hyperpigmentation and lichenification of the ventral neck and axilla of a crossbred with atopic dermatitis.
Fig 2 - Alopecia with hyperpigmentation and lichenification of the inguinal area of a West Highland White terrier with atopic dermatitis.
Fig 3 - Alopecia with hyperpigmentation and lichenification of the forelimbs of a Boxer with generalized demodicosis.