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The art of shampoos in veterinary dermatology

by
01 February 2013, at 12:00am

discuss the various types of veterinary shampoos available and what they contain and explain how they should be used

TOPICAL therapy is important in the management of many dermatological conditions as the skin is easily accessible to medications.

Amongst other topical treatments, shampoos are nowadays widely used by veterinary dermatologists. But the suitability for a shampoo must take into account the nature and extent of the lesions, the animal’s characteristics and temperament, climate and season, and owner’s technique and time availability.

What is a shampoo?

A shampoo is an aqueous solution, composed of surfactants (cleansing agents, foaming agents and conditioners) as well as thickeners, softeners, sequestering agents, preservatives, fragrance and sometimes opacifiers and colouring additives. In water, surfactants form micelle structures allowing them to emulsify, render soluble and disperse oils, dirt and debris.

Shampoos are ideal vehicles for active ingredients to treat the haired and sensitive skin of dogs. They penetrate the skin through the intercellular spaces, the epidermal cells and above all through the hair follicles in animals, particularly for ionised molecules (Figure 1).

How to use veterinary shampoos? 

A shampoo with both cleansing and therapeutic properties should be ideally applied twice at each use. The mechanical effect is beneficial in all cases. Water rehydrates the stratum corneum although this effect is temporary in the absence of moisturisers.

A shampoo can be used in a limited area or more commonly all over the body surface. At the second application, the shampoo must be left on for several minutes (five to 15 minutes according to choice of product, concentration, type of base, and the skin condition), to allow the active ingredients to be properly absorbed and reach adequate levels in the deep cellular layers.

Moreover, prolonging the action of active ingredients has been made possible with liposomes, micro-emulsions and/or Spherulites3. The skin should then be rinsed thoroughly, for at least five minutes, to prevent irritation and to enable the skin to become adequately hydrated.

The therapeutic shampoo may be applied several times a week for two weeks. The frequency is then reduced to give the longest interval over which treatment is still effective, usually about one to two weeks.

Moisturisers (lactic acid, glycerine, propylene glycol, urea and/or chitosanide) should ideally follow each shampoo as they lubricate, rehydrate, soften the skin and restore an artificial superficial skin film.

Shampoo therapy in keratoseborrhoeic disorders

Shampoos designed for the treatment of keratoseborrhoeic disorders contain keratomodulating agents which work in two different ways.

One way is restoration of normal keratinocyte multiplication and keratinisation with agents mainly keratoplastic/keratoregulating: sulphur, selenium disulphide, ammonium lactate.

The other way is the elimination of excess corneal layers with agents mainly keratolytic like salicylic acid associated with sulphur. Sulphur alone, selenium disulphide and ammonium lactate also have keratoregulating properties. Phytosphingosine could also help restructuring the stratum corneum.

Keratomodulating shampoos also contain antiseborrhoeic agents (sulphur, selenium disulphide, zinc gluconate, vitamin B6 associated with zinc, phytosphingosine, benzoyl peroxide) which inhibit or reduce sebum production by the sebaceous glands, and help clear the ducts. Some of them can cause a rebound effect.

Some shampoos can contain essential fatty acids and/or moisturisers such as glycerine, lactic acid and fatty acid polyesters.

The therapeutic agent often needs to be changed following the development of side effects, rebound effects or changes in clinical presentation. Long-haired dogs with severe seborrhoeic disorders may be clipped.

Shampoo therapy in canine bacterial pyoderma and bacterial overgrowth

There is little scientific evidence of efficacy of antiseptic ingredients available in shampoos based on randomised, controlled clinical studies, although there are numerous reports documenting their in vitro antimicrobial efficacy.

But there is evidence that the mechanical cleansing with shampoo vehicle or water decreases bacterial count16, and also removes tissue debris and exudate, allowing direct contact of the active ingredient with the organism.

Only benzoyl peroxide, chlorhexidine and ethyl lactate were evaluated widely in in vivo and in vitro veterinary studies, and there is good evidence, from in vivo studies, for recommending the use of shampoos containing chlorhexidine 2% to 3% as the first choice.

Benzoyl peroxide at 2.5% can be recommended, although it was found to be less effective than chlorhexidine. Acetic acid combined with boric acid and ethyl lactate at 10% may be useful too. Moreover, glycotechnology is an interesting concept which has been applied to shampoos to fight microbial invasion by blocking microbe adherence on host skin.

Mild cases of superficial pyoderma can be treated with shampoos alone. However, in most cases systemic antibiotics will be administered, the shampoo playing a supporting role.

It may have a prophylactic effect if used regularly. In cases of deep pyoderma, clipping is preferable to prevent the formation of a sealing crust and allow the product to contact the lesions.

Shampoo therapy in fungal diseases 

Antifungal shampoos reduce the infectivity in cases of dermatophytosis but are not effective in treating it as sole therapy. When associated with systemic therapy, they can speed up the clinical and/or mycological cure.

In Malassezia dermatitis, topical therapy is clearly an alternative to systemic treatment. Shampoos containing a combination of chlorhexidine and miconazole (2% each) showed good evidence for recommending its use.

Recently, a 3% chlorhexidine shampoo was shown to be as efficacious as the 2% miconazole-2% chlorhexidine one in dogs with Malassezia dermatitis. Glycotechnology can also be applied to shampoos to fight yeast infection.

Shampoo therapy in allergic diseases

Bathing weekly with a mild non- irritating shampoo and lukewarm water should be beneficial for allergic dogs, with a direct soothing effect to the skin, the removal of surface allergens and microbes, and skin hydration.

A micro-emulsion shampoo, specifically designed for canine atopic dermatitis, containing lipids, complex sugars and antiseptics, has been shown to be effective.And when used in a whirlpool, the antipruritic effect was more pronounced.

Actually, there is currently no evidence of any benefit from using other shampoos or conditioners containing ingredients such as oatmeal, pramoxine, antihistamine, lipids or glucocorticoids.

Conclusion

Communication with owners is important and should underline the great value of medicated shampoos for the treatment of skin diseases in animals with a haired skin. The therapeutic plan should be then defined on both a short- and long-term basis to obtain the best results, to enhance the owners’ compliance and to limit potential side effects.