Shampooing dogs: facts and myths

How often should dogs be bathed?

One of the most frequently asked questions – and a question that has many answers, many of them not necessarily the right ones! What is so obvious yet very often overlooked is the simple fact that dogs are not suited to the human environment. They are, essentially, naturally outdoor creatures; the dog’s skin physiology is not designed to cope with the environmental stress
caused by dramatic fluctuations in temperature and humidity
produced by central heating. Routine shampooing, using a properly formulated shampoo, can counteract some of these chronically deleterious effects.

What is “doggy” smell?

It is a sad fact that the majority of dogs do carry some degree of doggy smell. Many people seem to get used to this and it is only visitors to the home who notice the smell and often find it quite offensive. Natural sources of dog odour come from three sources:

1. the mouth – the level of odour being directly proportional to the degree of dental disease;
2. a small area between the anus and the genital area where there are often some exotic bacteria that produce some weird and not so wonderful smells;
3. the skin itself which accounts for the vast majority of doggy smell – this smell is caused by the rancidification of fatty acids on the skin and can produce quite intense odours.

The fact remains that dogs should not smell quite as much as they do but strangely this phenomenon is accepted by most dog owners; it is not “normal”!

What are the problems caused by the home environment?

Many dogs suffer chronic drying of the skin caused by the dryness of centrally heated homes. In its simplest manifestation this will lead to chronic scaling or dandruff. Ultra short-haired breeds such as Dobermanns are especially prone to this. Furthermore, in our homes we surround ourselves with a plethora of manmade fabrics such as nylon and polyester. When the dog’s fur comes into contact with these artificial fabrics
there is a tendency to produce a significant increase in the naturally negative static electrical charge on the fur coat.
House dust (accumulated skin cells from humans and pets) carries a natural positive electrical charge so is actively attracted to the dog’s coat. Unfortunately, house dust mites, one of the commonest causes of allergic skin problems in dogs, which feed on house dust, are also electrostatically attracted and concentrated on the skin in the same way – which may cause significant clinical problems in many dogs over a period of years.

So how can routine shampooing help?

Effective shampooing, using the right product, will do the following and therefore help to keep the skin odourfree and in good condition:

1. Cleanse the skin – it will remove stale or rancid fatty acids and therefore reduce odour; it will also remove the skin debris, i.e. dead skin cells, that may accumulate and block pores or follicles.
2. Promote the proper production of the natural skin oils in the sebaceous glands and allow these to flow freely across the skin to help keep it moist and supple.
3. Condition the skin and hair.

Conditioning is a generally poorly understood term. In this context it means two things: reducing the static electrical charge and thereby reduce the attraction of dust and dirt to the
skin, and close up the scales on each individual hair shaft which makes the hair reflect the light so it shines and looks good, as well as reducing the potential “purchase” opportunity for dust and dirt to settle on the hair.

How often should a dog be bathed?

There is no simple answer to provide the ideal solution for each situation. However, simple awareness of the above issues is a good starting point. One’s nose is a good indicator: if the dog is a bit whiffy then it’s a good time to bath it! Certainly, if the dog has dandruff it needs help and some simple but properly formulated shampoos may be all that is needed. Some dogs may only need a bath every few months while some may need bathing twice a week or more.

Can human shampoos be used?

A very simple but firm answer is: no – never! This is because the pH of human skin is acidic (pH 5.5 to 6.5) and all human shampoos are formulated to take this natural acidity into account. The pH of dog’s skin is mildly alkaline – pH 7.5 to 8 or slightly more in some areas. It is therefore obvious that human shampoos are very definitely not to be used on dogs – they are the wrong pH! The use of shampoos in dogs There is a series of fundamental goals aimed at the routine maintenance of healthy skin or in the successful alleviation of a variety of skin disorders:

• control surface micro-organisms;
• remove crusts and scales;
• restore epidermal turnover rate to the norm, i.e. 21 days;
• restore correct hydration, i.e. water balance, in the skin;
• remove parasites;
• remove allergens.

Medicated, suitably formulated shampoos when used properly are ideally suited to provide fast and effective relief of clinical signs associated with scaling and pruritic skin disorders. To benefit from shampoo therapy, it is important to know the types of shampoo available and when they should be used. Proper use of shampoos is of utmost importance to achieve the maximum effect. First, contact time of five to 15 minutes allows for hydration of the skin and provides sufficient time for penetration and action of the shampoo ingredients. Water in itself is an excellent skin hydrator, but if not left on long enough, evaporation and drying of the surface layers of the skin may result. Too long a contact time will result in the “dishpan hands” syndrome, whereby the skin becomes macerated. It is difficult to judge time, especially when a wet, soggy, 60kg Newfoundland is ready to shake and fight in order to get out of the tub. An egg timer or watch should be used to monitor the contact time. The frequency of bathing is also important. While common sense would dictate that the time to bathe a dog is when it is dirty, the interval between bathing is based on the presence of skin disease as well as the shampoo being used.
Commonly, shampooing may be required two to three times a week until adequate control of scale, grease and odour is achieved. Thereafter, a maintenance frequency of once weekly
or once monthly may be all that is needed. Maintenance shampoo therapy is also dictated by seasonal influences. Variations in heat and humidity affect dryness, scaliness, greasiness, and the tendency to develop secondary bacterial infections. Lastly, shampooing technique must be considered. The mechanical process of shampooing is beneficial in that it helps to remove crusts, scales, dirt, organisms and residual medication. All too often, however, the underside of the pet, which is frequently the most severely affected area, is neglected. Shampooing the entire pet and rinsing thoroughly will provide optimal results and decrease the irritating effects shampooing might have. One must bear in mind that shampooing rarely cures a skin condition. In some cases, cure is not possible, e.g. canine atopic skin disease, or the deep root cause could be, for example, a complex hormonal disorder. Before we move on to the specific shampoos for specific skin conditions, let us make clear some definitions of some of the terminology used in dermatological therapy and then we will look at the ingredients used in shampoos:

• keratolytic – removes top two or three layers of squames;
• keratoplastic – slows down rate of reproduction of basal cells at the base of the epidermis;
• emollient – softens and soothes the skin;
• humectant – moistens or moisturises the skin;
• conditioner – reduces static electricity and adds “body” to hair by closing up the scales on each hair shaft, making them reflect the light so the hair coat shines;
• astringent – causes contraction of small blood vessels and so stops secretion or “weeping”.

THE SHAMPOOS:

What’s in them and why? Benzoyl peroxide (BPO)

• keratolytic – removes at least top two or three layers of squames from the skin surface;
• follicular flusher – washes out oils and debris within the hair follicles (really deep cleanser);
• potent antimicrobial – kills bacteria/fungi/yeasts very rapidly on contact;
• potent degreasing agent;
• main use – pyoderma: good idea to use with humectant as BPO is very drying so there is a requirement to put back the moisture that BPO will take out;
• never use where skin is dry in first place.

Sulphur

• keratoplastic – restores epidermal turnover rate to normal;
• keratolytic;
• follicular flusher (mild);
• antimicrobial – bacteria/fungi/yeasts;
• anti-pruritic;
• main use – scaling defects (seborrhoea). Salicylic acid
• keratolytic;
• bacteriostatic, i.e. stops bacteria from reproducing;
• anti-pruritic (mildly);
• main use – scaling defects (seborrhoea): frequently used in combination with sulphur in shampoos designed to combat scaling disorders.

Urea/lactic acid

• hygroscopic – attracts water to skin;
• emollient;
• humectant;
• lactic acid mildly antibacterial;
• main use – mild, dry scaling defects (seborrhoea); routine rinse/spray to keep skin hydrated.

Piroctone olamine

Developed in the human pharmaceutical industry as an effective anti-dandruff agent (dandruff in humans is caused by a cousin of our Malassezia fungus – Malassezia furfur).

• potent antibacterial activity and is active against a wide range of Gram +ve and Gram –ve bacteria, including Staph. intermedius;
• potent fungicide – active against fungi such as Malassezia spp. Ethyl lactate Breaks down on contact with the skin to form:
• lactic acid (see above);
• ethanol – potent bacteriocide;
• main use – surface pyoderma, i.e. mild bacterial skin infections.

Oils – glycerine, propylene glycol

• cosmetic – apply shine, useful for dog/cat shows;
• prevent water loss through skin so useful for dry skin conditions;
• conditioning – these oils are naturally positively charged so tend to neutralise the natural negative charge on the hair coat;
• humectant;
• main use – good looks and routine conditioning/management of dry scaling conditions.

Chlorhexidine

• n antifungal;
• n antibacterial – has a useful residual effect in that chlorhexidine binds to keratin and a single application can last for several days;
• n generally well-tolerated;
• n main use – pyoderma.

Miconazole

• ntifungal – active against Malassezia;
• main use – Malassezia dermatitis, severe greasy scaling disorders.

Olefin sulphonate

• well-tolerated, tried and tested cleanser; non soap compound hypoallergenic;
• main use – routine cleansing.

Hamamelis (witch hazel)

• astringent;
• main use – “hotspots”: highly irritated, pruritic small areas, often caused by insect bites in the summer months.

Oatmeal

• anti-pruritic – often used in human medicine for the treatment/relief of psoariasis;
• main use – general soothing shampoo, especially useful in the relief of flea allergy dermatitis.