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.
