Assistant Professor of Veterinary Dermatology, University of Georgia, Athens, GA, USA
Over the thousands of years during which we domesticated our animals, they have become our companions, which we share our houses with. Living closely together with our pets, we place increased value on their appearance. The hair and skin of our pets has become more of our focus. We want a companion who has a shiny hair coat, clean appearance and pleasant odor.
The normal skin surface film consists of excretory products of the skin glands, some corneocytes and keratinocytes as well as mix of bacteria, pollen, grains, and mold spores. Especially if these last components increase in number, the hair coat can become less shiny and may look dirty.
A shampoo used for routine bathing should be able to remove these accumulations on the skin surface and prepare a soft shiny hair coat, which is easy to comb.
Besides removing the dirt from the skin, a shampoo also removes the natural oils. This raises the question of how often a dog can be bathed without adverse effects such as dehydration and when conditioners should be used to keep the skin moisturized. In less humid it is suggested to bath no more frequently than once per month. In more humid areas, it becomes less likely that more frequent bathing (2–4 times monthly) will excessively dry out coats and skins.
Also, it may not be necessary to use shampoos with every bathing. For example, the young dog who likes to play in the mud may be rinsed with warm water only to remove the dirt and a shampoo may only be used with every other bathing, which will allow the skin to keep its moisture much easier.
For a routine bath the dog should be rinsed with warm water first and then the "right amount" of shampoo should be applied, massaged into the whole hair coat and rinsed off thoroughly after 5–10 minutes. The "right amount" of shampoo is greatly dependent on the product, and its lathering ability. A thorough rinsing time is not only important to eliminate the shampoo, which could be irritating for the skin. It also gives the skin the chance to re-hydrate.
Shampoos used for routine bathing purposes.
Recall, a little goes a long way; excessive amounts will result in the need for longer rinses
Very mild, but often do not lather well and therefore may require more shampoo.
From reputable pet store or veterinary clinic
Difficult to recommend. Many are pH regulated for human skin (more acidic than skin of dogs); whether this is a problem or not is not known.
I) Therapeutic Shampoos
In veterinary medicine, shampoos are used on a regular basis for several different conditions. Canine skin is often more sensitive than is human skin due to anatomical and physiological differences, including differences in the thickness of the stratum corneum, skin pH and hair follicle density which can facilitate cutaneous penetration of active ingredients. The active ingredients penetrate the skin through the intercellular spaces (lipophilic molecules), through the epidermal cells (ion compounds). Several formulations such as ointments, creams, lotions shampoos, spot-on, etc. are available and may include many active ingredients. For successful topical management the selection of the appropriate formulation and active ingredient is important. However, the selection may depend on concurrent therapy, the animal's temperament owner compliance, and the concentration and potential side effects of the active ingredients. Client communication is important and should underline the great value of medicated shampoos for the treatment of skin diseases. The frequency of bathing is defined by to components, the therapeutic time span of the used product and the time the owner is able and willing to spend on bathing his animal on a regular basis. In general a bath with a medicated shampoo will take around 20–30 minutes, not including the cleaning time for the bathroom or the time it takes to convince the young, wiggly Golden Retriever to enter the bathtub and to stay there... and to clean the bathroom afterwards...Two to three bathes per week will in general be the maximum the patient and owner are able and willing to do.
General bathing procedure
1. Especially if the patient's skin is dirty, the dog should be shampooed/rinsed initially with a less expensive dishwashing liquid or grooming shampoo to remove grease, debris and dirt. As a result, the medicated shampoo will have a better contact with the skin. Less therapeutic product will have to be used and less expense will incur.
2. Contact time is of paramount importance, since it allows the active ingredient to do what it needs to do on the surface of the skin. Standard recommended contact time is 5 to 10 minutes (i.e., lather well, leave on for 5–10 minutes and rinse well). It is important for the owners to use a [sic]
3. Thorough rinsing is mandatory, because many of these therapeutic shampoos, if left on the skin, may be irritating. The skin gets its chance to re-hydrate again.
It may be helpful to actually use a clock, to determine the correct amount of time for each bathing step. Time can pass very slow, especially if our young Golden Retriever is not very cooperative.
A. Antiseborrheic Shampoos
Seborrhea is a term used to describe an abnormality of either keratinization or cutaneous lipid production, or more commonly, a combination of both.
There are two morphologic forms of seborrhea, which may be seen in combination on the same animal.
The most common form of seborrhea seen in the domestic species is seborrhea sicca. Animals are usually presented with a dry skin, focal or diffuse scaling (white or grayish, usually non-adherent scales). These findings imply a decreased sebum production although much of the dryness may be due to epidermal dehydration. Occasionally thick, hyperkeratotic scales or "tags" are noted to be adherent to the skin or hairs.
Seborrhea oleosa patients present with thick, tenacious, yellowish, "oily" accumulations, which are odiferous. This implies excessive sebum production. The coat often appears to be dull because of abnormal light refraction.
The signs of seborrhea may be complicated by hair loss and usually mild pruritus, which is due to severe dryness or abnormal sebum production. Secondary bacterial infections caused by changes in the cutaneous microenvironment may also contribute to the development of pruritus.
Generally, antiseborrheic shampoos are keratolytic, which means they peel the superficial epidermis, and cause swelling of the surface corneocytes so that they are more easily removed during the shampoo process. They are also keratoplastic, which means that they normalize the keratinocyte/epidermal turnover.
Common ingredients in anti-seborrheic shampoos
(Listed in order of increasing keratolytic, degreasing and drying potential).
Often used in conjunction with salicylic acid
Also very good antibacterial effects
Also has some anti-pruritic effects. Tends to have a disagreeable odor and lathers brown! Some coal tar products have been more highly refined to reduce these aesthetic problems, but these products do not appear to be as efficacious. Overall, coal tar seems to have been replaced in most countries by newer antiseborrheic products, which work as well without the odor and staining
No veterinary products available at this time
Good keratolytic and keratoplastic activity. Used in combination with moisturizing ingredients
Pro-ceramide in the epidermis with restructuring as well as antiseborrheic and antimicrobial effects.
The frequency of bathing depends on the severity of seborrhea; initially a bath every 7 days is usually sufficient. However, if dealing with a very severe seborrhea oleosa, a bath every 3–4 days may be indicated initially before tapering to weekly shampoos.
In general it has to be kept in mind that repeated shampooing removes surface oils, thereby predisposing the skin to dehydration. Dehydration potentiates seborrhea sicca and pruritus. So, the use of moisturizers or conditioners following shampoos should always be considered when treating seborrhea sicca and in cases of seborrhea oleosa, once the condition normalizes.
B. Germicidal Shampoos
1) Antibacterial Shampoos
In small animal practice, antibacterial shampoos are most commonly used as adjunctive therapies to systemic antibacterial therapy, to hasten the resolution of problem and to aesthetically improve the coat/skin. They are often used once weekly. It is possible to resolve a bacterial skin infection (especially milder, superficial infections) with just a shampoo, but best response to exclusive shampoo therapy is seen with superficial infections (e.g., impetigo in a puppy) and increased frequency of application (e.g., 2–3 times per week).
Frequently used antibacterial ingredients:
Benzoyl peroxide: excellent antibacterial shampoo ingredient that also has degreasing and antiseborrheic (keratolytic) properties and may have so called "follicle flushing" capabilities. Its antibacterial action results from its ability to oxidize substances and has been shown to last for as long as two days.
Potential deleterious side effects: excessive drying of the coat/skin. A small percentage of dogs may be irritated by this product. This percentage is somewhat higher for cats. Benzoyl peroxide breaks down with time; we must heed expiration dates and purchase from well-known, reputable companies.
Chlorhexidine: biguanide with antibacterial, antifungal and antiviral activities. It is not inhibited or inactivated by organic debris (dirt, scale, crust). Chlorhexidine is noted for its residual properties (lasting as long as 2 days). The product is nonirritating and nontoxic. More concentrated preparations appear to be associated with superior effects (i.e., 4% is better than 3% which is better than 2%). It is often used as a milder shampoo for dogs with pyoderma that have drier coats and skins (less likely to dry out than benzoyl peroxide), especially for long term therapy.
Ethyl lactate: This ingredient becomes effective by breaking down into two compounds within the skin, lactic acid and ethanol. Lactic acid acts by decreasing the skin's pH and thus inhibiting bacterial lipases, whereas ethanol renders fats soluble and decreases the amount of sebaceous secretions. The half life of these products in skin is very short. Irritation, erythema, pruritus are infrequent side effects.
Triclosan: This antibacterial agent is added to many antiseborrheic shampoos to extend their spectrum of activity (i.e., provide more antibacterial properties).
Povidone iodine: Povidone iodine has antibacterial, antifungal, activity that works by iodinating and oxidizing sulfhydryl compounds, peptides, proteins, enzymes, vitamins, lipids and cytosine found in the cytoplasm and cytoplasmic membranes. Povidone iodine has a relatively short residual activity (4 to 6 hours) and is inactivated by organic debris (e.g., dirt, crusts, scale). Povidone iodine may cause contact dermatitis, skin irritation and staining. It is for these reasons that products containing povidone iodine have fallen out of favor in small animal dermatology. However, they remain a mainstay of therapy in large animals for topical therapy.
Acetic/boric acid: Mild antibacterial effects
2) Frequently used antifungal ingredients
Miconazole: Imidazole that exerts its antifungal properties by inhibiting ergosterol synthesis (essential component of the fungal cell membrane). Used as an adjunctive therapy in the management of dermatophytosis but with questionable efficacy. Usually used twice weekly for this purpose. It may help hasten the resolution of dermatophyte problems when used in conjunction with appropriate systemic treatment and may help decrease contagion through the removal and inactivation of arthrospores. Miconazole shampoo can be used as a sole treatment for Malassezia. It is more effective if combined with chlorhexidine. Initially used once every 2–3 days for 2–4 weeks to control problems. Expect to resolve 50–60% of cases with this regimen.
Ketoconazole: Effects as for miconazole.
Selenium Sulfide: Used for Malassezia dermatitis (once every 2–3 days for 2–4 weeks).
Acetic/boric acid: Used for Malassezia dermatitis (once every 2–3 days for 2–4 weeks).
Chlorhexidine: mild antifungal activity for dermatophytes and Malassezia
Povidone iodine: moderate antifungal activity for dermatophytes
C. Antipruritic Shampoos
Antipruritic shampoos are noted to produce transient benefits with respect to pruritus (hours to at most a day or two).
Oatmeal: Exact mechanism unknown, but has been suggested that oatmeal inhibits prostaglandin biosynthesis. Benefits may last from hours to a day or two.
Pramoxine: Topical anesthetic; duration of effects as for oatmeal. Often used in conjunction with oatmeal in various products.
1% hydrocortisone: Antipruritic effects about equal to the oatmeal/pramoxine products available; may have to do with dilution of the hydrocortisone that occurs during the shampooing process.
D. Antiparasitic Shampoos
A number of these products are available. They generally contain pyrethrins, pyrethroids or carbamates. They are usually marketed as flea therapies, with efficacy for other ectoparasites as well. For fleas, they often produce good knockdown, but have no residual activity. They are usually safe for use in young puppies and kittens. They are generally weak therapies for ticks. They may be effective enough to be a sole treatment for louse infestations.
II) Moisturizing Ingredients
Emollients are agents that soften the skin. In large part, this is done by filling in the spaces between keratinocytes with oil, providing a waterproof layer on the stratum corneum. Water moving upwards from the dermis is trapped, and the tissue softens.
Examples of emollients include oils (almond, corn, cottonseed, coconut, olive, peanut, Persia, safflower, sesame) and animal fats (e.g., lanolin from sheep wool).
Emulsifiers are often added to emollient solutions to help distribute the oils into a water solution; this makes the oil solution more effective because it can spread more evenly over the skin's surface.
Examples of emulsifiers include acetyl alcohol, laureth-5, lecithin, PEG-4, dilaurate, stearic acid and stearyl alcohol.
Humectants arehygroscopic, water-absorbing materials. Humectants act to rehydrate the skin by attracting water from deep within the skin toward the surface.
Examples: propylene glycol, glycerin, colloidal oatmeal, urea, sodium lactate, lactic acid, sorbitol solutions, carboxylic acid, polyvinylpyrrolidone.
Frequently Used Products
Oils:Following rehydration, oils (mineral oil, lanolin etc) form a barrier to prevent rapid dehydration. Rehydration ideally accomplished by soaking animal in tub for 5–10 min. Significant rehydrating will, however, be provided through simple shampoo and rinse process.
Propylene Glycol: Rehydrates by binding water to epidermis; draws water into epidermis from deeper tissues. Only minimal "oily" consistency.
Conditioners contain various oils/fatty acids, often along with other active ingredients (e.g., oatmeal or pramoxine for antipruritic effects). These products de-tangle hair and help return softness and luster to the coat. They may also serve as a "barrier" to help retain moisture within the epidermis. They are used following anti-seborrheic or antipruritic shampoos or as rinses between shampoos.
There are two types of products available. The first one has to be rinsed away following application. The other form of conditioners are applied to a wet coat and left on to dry (so called "Resi" conditioners). These appear to be associated with the best residual effect of added ingredients (e.g., oatmeal, pramoxine or hydrocortisone etc.).
To extend the efficacy of their products various techniques have been developed:
Novosomes - Novosomes are stable, microvesicles (type of liposome) with five to seven bilayers and a central holding area, 80% of which is comprised of water and/or lipids. The inner solution within the cargo area is slowly released as the various layers break down (requiring 7 to 10 days in average temperature conditions).
Spherulites - Spherulites (Virbac) are composed of multiple layers (10 to 1000) of plant-derived surfactants and are 1 micrometer in diameter. The shampoo ingredient within the Spherulites is slowly released (over 8 days) as the different layers of the Spherulite break down. Moisturizing agents, essential oils and water and fat soluble vitamins can all be encapsulated in the same Spherulite. Spherulites also contain chitosanide - a multipurpose glycoprotein derived from chitin (crustacean shells) - which helps to form a film coating over the skin and hair. Chitosanide tightly binds the spherulites to the hair and skin by providing chemical differences in positive and negative charges.