Clipping the dog short for the summer-a look into the scientific literature

I wrote a long blog post 4 years ago about clipping dogs short for the summer -especially so-called double coated breeds. (https://wordpress.com/post/theeducatedgroomer.com/4)
It took me one year to put it all together and it has had over 100 000 views just past its 4th anniversary.
I never thought it would get that popular, my main goal was to have a page to refer to in discussions about the subject.

I have throughout the years come to realise that some people find it a bit too overwhelming with all the information and I have therefore decided to revamp it to make it more accessible. I have also updated it with new scientific papers that have been released since I wrote the first post and others that I have found during my research.

It is hard to shorten it as this is not a black and white subject that you can deal with in a simple Facebook meme…..You need all information to fully understand the complexity.

I have tried my best to make it a bit easier to digest the information – but I am sorry to say that it’s still as long – SORRY!

What I have done now is to have a short summary at the start of each “chapter” that is done in italic writing and then a more in-depth section for those who want to dig deeper into the subject. All references are in the in depth section. If you don’t want to read everything – just read the introduction for each section and skip the rest.

Let me know how you find it 😊

There is no easy answer and we can’t just base the decision we make on a Facebook meme

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Welcome to Clipping the dog short for the summer 2.0 !

Every summer comes the heated debate about clipping dogs short for the summer- and it´s especially the so-called double coated breeds that cause a stir.
 The debate has been going on for ages and it is like a religious debate where you have 2 fundamentalists discussing whose God is the right one.

It’s been flaring up on the internet in different forums long before Facebook. But with Facebook, there is an added element of different “factual” articles being shared. Mostly from the No side and they all claim to show why it is wrong using different claims that very seldom have any scientific backing.

The latest one is a thermal camera picture of what we are told – a golden retriever in a lion trim and the claim is that we could see in the picture that the clipped area is warmer than the longhaired one and that proved that it was bad to clip them.

Another interesting fact during the discussions is that most of the claims only apply to so-called double-coated breeds. Apparently clipping a poodle with a 5F or stripping a border terrier down to its undercoat is fine – but loads of bad things will happen if you clip a “double-coated” breed. The logic is gone – they are all dogs and the same rule for thermal regulation applies to all of the – so-called “double-coated” breeds are no magical creatures that have their own set of rules.

So, what is right? Will they die from heatstroke if we clip them as we mess up their thermoregulation? Will they get burnt by the sun and get skin cancer? Are we causing them unnecessary suffering if we clip them? And will the coat be destroyed and never grow back again?

As a former vet nurse now grooming my world is ruled by scientific facts – not myths/old housewife tales – so I decided to dig into the subject from the scientific point of view – gathering facts produced by professionals rather than from various written pieces from laymen like dog rescues or Jane Doe that decided that they wanted her 15 minutes of Facebook fame.

I am going to try to explain how it works and then it is up to you as a groomer/owner to decide if you want to do it or not.

All claims that I do will be supported by information on where I found the facts so that you can check it out yourself. I urge you to do that -click on the link under the study and read it yourself – that will give you more information on the small details.
If the study is hidden beside a paywall – copy the long doi.org number that is under the title of the paper and paste it into www.sci-hub.se – that will give you free access to the paper.
Then you will be able to do an educated decision based on proven scientific facts instead of asking on Facebook and getting someone’s view that is based on a myth passed down for generations.

The fact is that science changes as well – what was thought to be the truth 15 years ago, could now be proven wrong with new facts emerging.

One thing that makes this subject so complicated is the fact that we must deal with 2 different factors- the physiology part that clearly says one thing and the dermatological part that might say another thing depending on the coat type.

We must learn to separate them to start with in order to understand the subject better, and once we have the knowledge of both factors, then we can make a decision.

         My take on this subject from the start was quite clear and black and white – but while digging into it I realized that is more complicated than I thought, and I had to review my standpoint a bit. It is not as easy as any of the side claims ….. it’s a complicated issue that depends on a lot of factors and this is why this piece is looooooooooooooooong……..

I have tried to use a layman’s language so it’s easy to understand even if you don’t have any medical training. So grab your coffee and a box of chocolate and start to read – it is going to be a long journey …

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Let’s start with that thermal image of the clipped golden retriever 🙂

 “A thermal picture show how much heat that is radiating FROM THE SURFACE of the dog- not the dog’s body temperature or how hot it is inside the coat ….. and it will of course be more heat coming from the short clipped area than the long-haired one as the coat insulates and KEEPS the heat from slipping away from the skin.
It will be the same if you took a picture of a  greyhound with a towel over its front  – the area with the towel  will display a lower temperature as the fabric will block some of the heat that you see on the bare skin
But if you put the dog out in the sun, the radiation from the sun will heat the surface and the temperature you see will now be much higher on both the bare and the covered areas “


So, the picture showed that the coat was doing its work properly – it kept the heat from leaving the dogs skin while the clipped area was allowing heat to leave the body faster. It actually showed what the Pro side says – clipping dogs keep them cool as it allows heat to leave the body.
And if you think about it, how is it possible for a dog to have different body temperatures in different parts of the body? You can of course have different surface temperatures, but that doesn’t determine the core/body temperature.

Studies of thermal imaging show that long-haired and double-coat dogs had lower surface temperatures. That’s because the heat inside the coat cant get out onto the surface and therefore won’t affect the surface temperature.
Rectal temperature was not significant in evaluating differences in surface temperature. Showing that a thermal image wont tell you if a clipped dog is hotter than a unclipped dog. It only shows the difference in the surface temperature.

 To learn more about how thermal imaging of dogs works -read these papers:
Mari Vainionpää Thermographic Imaging in Cats and Dogs Usability as a Clinical Method,2014 https://core.ac.uk/download/pdf/20441286.pdf
Quantifying body surface temperature differences in canine coat types using infrared thermography
https://www.sciencedirect.com/science/article/abs/pii/S0306456518305503

You can also read more on Wikipedia  https://en.wikipedia.org/wiki/Thermography

Here is an illustrated explanation on the subject from Dr Melissa Starling:

” Thermal cameras detect infrared radiation and convert it into an image. Radiation increases with temperature, so these cameras can be a nifty tool for looking at temperature. However, they do not measure temperature per se. They measure radiation. For example, the image below is of my short-haired dog Kestrel in a cool environment. At the time, Kestrel had a shaved belly due to her recent sterilisation surgery. You can see clearly where her hair was clipped because it is much warmer than the rest of her.

This doesn’t mean that it’s the hottest part of her. Other parts are covered in a thin layer of fur, and even that is enough to reduce the amount of body heat she radiates, as it traps some of that heat against her skin where the camera cannot “see”. Her extremities are quite cool, which probably does reflect her skin temperature in comparison to, say, her back, which also has a thin layer of fur. The second picture is of Kivi in the same environment, who has a great deal of fur. His body has a lot of blues and greens, indicating he is radiating less heat than Kestrel is. This is the whole point of dense coats. His cooler coat does not mean he is cooler at this moment. It means his coat is doing a great job of trapping his body heat well away from the air and not a lot of heat is escaping from his body.

If the ambient temperature were a lot warmer, would this change his thermal image? I can’t show you an example, but yes, it would, to a degree. For example, if he stood in the sun, it would warm up his coat. Would that mean his skin and body were also warmer? Probably to some degree. We can see that some heat at least can escape his coat, so presumably, it goes both ways.”
( many thanks to Melissa for allowing me to use her pictures and texts. Visit her Facebook page about canine behaviour https://www.facebook.com/DrMelissaStarling/ )

That’s the dreaded golden retriever picture debunked – let us move on to the coat and thermoregulation. 😊

For us to be able to make good decisions ,we need to understand the basics of thermoregulation and the coats role in it

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How do dogs keep their body temperature at the right level?

( Read more in Guyton and Hall Textbook of Medical Physiology  and on Wikipedia
https://en.wikipedia.org/wiki/Thermoregulation#In_birds_and_mammals

Temperature requirements for dogs
  https://www.extension.purdue.edu/extmedia/va/va-16-w.pdf )

“ The system aims to maintain a core temperature of 38C and if it starts to go above it or below it different mechanisms kick in to either dissipate or gain heat. It’s like the heating system in your house. If the system fails to maintain the optimum level -damage will occur to the body and in the end death

Heat is lost  in the following ways :

Conduction -heat moves from a warm area to a cooler one – the dog can lay on a tiled floor and the heat moves from the dog’s body. It also happens inside the coat when the warm air move to an area with cooler air.
Convection – heat is removed by airflow – the wind blows over the dog or the coat opens up by the dogs movement and the heat is released from the coat by the air movement
Radiation– heat radiates out from the object – heat radiates from the skin
Evaporation– when a fluid changes to a vapour – when the dog pants and when sweating from pads and skin. When the fluid changes to a vapour ,heat is lost .

Heat is gained from the environment and muscle movement and processes in the body

If the heat input is greater than the heat output, the dog is at a high risk of heatstroke/heat stress  

To make it short – at lower environmental temperatures body heat is lost thru radiation from the skin and that heat is then trapped in the air layer that is in between the hairs in the coat. If it’s windy/the dog moves most of the heat will disappear when the hair moves if the condition of the coat allows it. The longer/thicker the hair is – the bigger the air layer is, and the more heat is trapped inside it and it’s harder for the warm air to disappear as conduction/convection won’t reach down into the long thick coat. If the air trapped in the coat gets chilled – the system kicks in and produces more heat as the sensors in the skin react to the difference between the body temperature and the environmental temperature.

The main heat loss thou is done by panting – panting is more important for the total heat loss and the shorter the face is on the dog – the harder it is for the dog to lose heat in this way. Fat acts as insulation in both ways – it prevents the heat from leaving the body and it keeps the body warm when the environmental temperature goes down“

All warm-blooded animals have the same basic thermoregulation system – dogs, cats, hamsters, humans, birds….. the basic is no different. Once you investigate different species there has been adaption done during evolution to adapt to the different environments/circumstances. But within the same species it’s all done in the same way  -so no difference between different dog breeds for example.

The body has an advanced system that is in charge 24/7 to keep the body temperature –core temperature – at a correct level. For dogs, this level is 38.5 ( +-0.5 ) When the temperature goes above or below that level the system kicks in to restore it to the correct level – more or less like your average thermostat in your boiler system or AC unit.

This system is not fully developed in young individuals and is less efficient in old dogs – so they are more vulnerable to changes in the surrounding temperature – both heat and cold.

It’s important to keep the core temperature at a correct level as the dog’s body is made up of cells that contain a vital fluid known as protoplasm. This protoplasm contains proteins and vital nutrients, enzymes, and hormones necessary for life function. Chemical reactions necessary for life are occurring in the cells and if the core temperature is too high or too low those reactions will be altered, and damage will occur to the whole body and in the end death as the system collapses.

Nature has put a great deal of thinking into the anatomy of animals to adapt to the environment they live in. You see for example that animals that live in cold environments are usually larger than animals that live in hot environments as it’s easier to keep the core temperature at a correct level in a larger body volume in a cold environment and vice versa.

The coating of the body – with feathers/hair is there to insulate and prevent heat loss and protect the skin. The hair insulates and prevents the heat from leaving the body – and you see an example of that on dogs that is from cold environments – they have small ears that are very hairy – and on the opposite – dogs from hot environments have large smooth-haired ears to make it easier for heat to evaporate from the skin.

You can also see that animals that are developed for cold climates have thicker coats than animals from warmer climates. Some dog breeds that are developed in warmer climates might have a longish coat (but it’s thin) compared to breeds that are developed in cold climates.
They also set a thicker coat in the winter to increase the insulation

“Many mammals increase their pelage in the winter season against the cold and increase the metabolic rate to meet the strong and growing thermal demands of their environments
(HART, 1956, 1961; HERoux, 1963 ; HERoux et al., 1959 ; IRVING,1964; IRVING et al., 1955: SCHOLANDER et al., 1950).

Domestic dogs, commonly used as experimental animals in physiology, also increase the amount of their pelage when reared outdoors in winter. “

Seasonal Changes in Heat Balance of Dogs Acclimatized to Outdoor Climate

https://www.jstage.jst.go.jp/article/jjphysiol1950/31/4/31_4_465/_article/-char/ja/

We must also remember that we have changed the breeds throughout the years to please our eyes.
This is somehow forgotten by the No side in discussions on the subject.

 This means that we in this discussion cannot categorically refer to nature’s plan with shedding, etc., as our breeding  has changed the dogs’ coats so that they no longer function as nature intended.
We have also moved dogs that are made for cold climates (with attached extra insulating coats) to warm climates that require thinner coats.

Nature had a plan for the dog’s coat and if the coats were still the same today, as they were when dogs were created- and the breeds where still in their original environment , then we wouldn’t have this discussion…….
Its worded very well in the book -Hair loss disorders in domestic animals by Lars Mecklenburg , Monika Linek,Desmond J Tobin

Domestication can be associated with changes in hair density, hair length, hair thickness, hair structure, and hair colour eventually resulting in a hair coat that no longer can fulfill all its functions necessary for a typical life under normal outdoor conditions. These changes have been caused by genetic alterations in intensely bred animals as the cat and the dog.

Natural coats will be much thinner during the summer and thicker in the winter. But we like a lot of hair -so we have been breeding for more and more hair on the dogs and they can’t tolerate the same amount of heat anymore as they did before.

Golden retrievers are a typical example of that – they used to have a coat that consisted of short thick wool and longer shiny guard hairs. When they got wet from retrieving birds in the water they dried quite quickly.  Nowadays they have heavy long coats consisting of lots and lots of long wool and it gets even more if you neuter them.

Neutering also causes changes in the coat growth cycle and changes the coat. Most breeds that we class as “double coated” get twice the amount of undercoat that nature intended and the undercoat can sometimes also be much longer than normal. The undercoat is not shedding in the same way it used to do, leaving the dogs with non-functional coats.

( Spaying-induced coat changes: the role of gonadotropins, GnRH and GnRH treatment on the hair cycle of female dogs Iris Margaret Reichler,Monika Welle,Christine Eckrich,Ursula Sattler,Andrea Barth,Madeleine Hubler,Claudia S. Nett-Mettler,Wolfgang Jöchle,Susi Arnold

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3164.2008.00652.x       )

    
We have messed up the system that nature once created – but nature hasn’t changed the thermoregulation system – it still works in the same way and now faces bigger obstacles with more hair that insulates the body.

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The dog’s body is creating heat 24/7 to uphold the ideal core temperature.
Heat is created by all the processes that are going on in the dog’s body – heartbeat, breathing, bowel movement and so on. It’s like a little motor going inside the dog 24/7- and just like a motor, it needs to be able to dissipate excess heat to avoid overheating.

To maintain a constant body temperature heat must be transported from the core of the body and released into the environment in several ways:

(Heat Production and Heat Loss in the Dog at S-36°C Environmental Temperature H. T. HAMMEL, C. H. WYNDHAM2 AND J. D. HARDY )
https://research.amanote.com/publication/4pY82nMBKQvf0Bhivs7m/heat-production-and-heat-loss-in-the-dog-at-836c-environmental-temperature

Conduction: occurs when the body is in contact with a cooler surface, thereby allowing heat to be transferred from the dog to that surface.  You can notice for example that dogs prefer tiled floors when it is warm rather than a fluffy carpet. Or they dig a hole in the ground and lay in it rather than on the grass. Most dogs have a thinner coat on the stomach, so it is easier for the heat to leave the body when in contact with a cooler surface –that’s why they lay flat on the stomach on the ground or on tiled flooring for example.
Some heat is also transported from the skin through the hair shaft to the outer layer of the coat if the environmental temperature is lower than on the skin.

Convection: the removal of heat from the body as air passes over it, as is seen with a fan or with wind or when the dog moves, and the hair moves. The movement of the hair allows the heat trapped inside the coat to escape. ( -if the dog is brushed so that the hair can move – a matted compact coat won’t move and therefore won’t release any of the heat )

The amount of heat that is released is depending on the length and thickness of the coat and the strength of the airflow. The longer /thicker the coat is – the less air is released. 

If you have a short coat – or no coat at all like us, humans – the wind will cool the skin as it passes over it unless the wind is warmer than the body. This is why it feels cooler to be by the sea on a sunny day compared to being stuck inside the city with no wind -even if the environmental temperature is the same.

Radiation: when the body releases heat into the environment.

When the body’s heat production is stable, the blood flowing into the skin is regulated depending on changes in the surrounding temperature. The purpose of this regulation is to ensure that the difference in temperature between the skin’s surface and the environment remains constant, thus regulating heat loss and maintaining an almost constant body temperature. When heat production increases, blood flow to the skin increases, which, in turn, increases the heat lost from the skin to the same rate as the excess heat production. Blood flow to the skin can vary depending on the requirement for heat loss or conservation. This blood flow is regulated by the sympathetic nervous system. An increase in core body temperature causes the blood vessels to expand, which in turn, increases the blood flow to the skin and therefore heat loss.

If the core temperature is getting too low the blood vessels shrink and the blood flow is decreased to minimize the heat loss.

A layer of air is trapped between the surface of the skin and the outer surface of the coat. Air has a low heat capacity and is a poor conductor of heat, therefore it serves as an insulator. The degree of insulation can be altered by increasing or decreasing the thickness of the air layer. This is achieved by a small muscle that is attached to each guard hair and makes it possible for the body to move the guard hair closer or further away from the body.  If you need more warm air trapped in the coat the guard hairs raise so that there is room for more air and if you want less air in the coat the guard hairs lay flatter to minimize the space. It is like when we get cold and get goosebumps and the hair on our arms/legs is standing straight out.

This means that heat is radiating from the skin into the air inside the coat and wraps the dog up in a warm bubble.This is good when its cold outside but will be a issue when its warmer temperatures.

Nature have thought about the issue with the insulating effect of the coat and created so called thermal windows where the coat is shorter/thinner so its easier for the heat to dissipate out into the environment if needed. You find them on the stomach,ears,front of the frontlegs and the lower part of the backlegs.
The skin is thinner in these areas and there is larger superficial blood vessels in the area to make it easier for the heat to leave the blood. When the core temperature is increased,blood is mainly directed to these areas.

(The effect of rate of heating and environmental temperature on panting threshold temperatures of normal dogs heated by diathermy , Allan Hemingway
https://journals.physiology.org/doi/abs/10.1152/ajplegacy.1938.122.2.511)

If the dog is fat the radiation will be less effective as the fat doesn’t transport heat well – so the fat will act as an insulation and keep the heat inside the body. (And keep the dog warm if it is cold) This is why arctic animals have a thick layer of fat to help them keep warm.

The first three mechanisms listed are only effective if the air around the animal is cooler than the temperature of the animal. At high environmental temperatures, the animal must solely rely on so-called evaporative cooling mechanisms: sweating and increased respiration

Evaporation: the process when a fluid is changing into a vapour. 
It happens in 3 ways in dogs – panting, sweating on the skin and sweating from the pads.
The sweating from the skin and pads is not a great contribution to the heat loss, panting is the main one.
Sweating in the skin can help to cool the skin and therefore contribute to the general cooling of the dog. When fluid evaporates it cools the surface as energy is removed when the fluid changes to a gas.  
( read more about evaporative cooling at
https://www.scientificamerican.com/article/chilling-science-evaporative-cooling-with-liquids/   )

This is the same thing that happens if you have been in the pool and get up – you can feel that your skin is cool as long as the water is on your skin. And if it’s a bit windy-then it feels even cooler.
But if the coat is long and thick, there won’t be any evaporation as the air inside the coat will be warm, and it won’t be any temperature difference between the fluid and the air.

As the environmental temperature increases above 32 C, evaporation becomes the most important way for the body to release the heat and the heat radiation from the skin becomes less effective. 

It happens in the soft tissue of the upper respiratory system and mouth and is increased by panting. The hot blood reaches the tissue in the nasal cavity and evaporation occurs when the hot blood heats up the tissue and that meets the cooler air. To keep the air in the upper respiratory system cool, the dog needs to pant when it reaches a certain temperature.

The main mechanism of heat loss during panting is water evaporation from the moist soft tissue in the nose. The heat of evaporation is removed from the tissues in the nose, cooling its blood supply. The cooled blood is collected in large veins and then passes through a small but dense network of blood vessels which functions as a heat exchanger, cooling arterial blood to the brain.

Under moderate heat stress, the dog pant with a closed mouth. Under significant heat stress, the panting increases and the mouth are open, and the tongue is hanging out to maximize the heat loss. The shorter the nose is – the harder it is for the dog to maximize the heat loss this way. The cooled blood then returns to the body core and that will reduce the core temperature.

If the relative humidity is also high, evaporative cooling is less effective and there is a high risk of heat stress.

If the environmental temperature is lowering the core temperature the body needs to create more heat.

One way is to shiver – this increases heat production as a chemical reaction called exothermic reaction happens in the muscle cells when stored nutrition in the cells is converted to energy. Shivering is more effective than exercise at producing heat because the dog remains still.  This means that less heat is lost to the environment via convection as the dog is not moving around.

They also raise their guard hairs to trap more air within the coat so that heat radiated from the body can keep the skin warm.

Muscle movement also creates heat, so moving around heats up the dog. This heat input will also go on for a time after the movement stops and this is why exercise can cause heatstroke several hours after the activity stopped. Movement is not an economical way of creating heat as it uses energy to move the muscles.

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Now when we know how the system works – what can we say about the effect of lots of hair on the dog?

“Contrary to the cold environments, increased insulation of fur is not beneficial to maintaining heat balance in warm environments. “

Seasonal Changes in Heat Balance of Dogs Acclimatized to Outdoor Climate
Yasuyuki SUGANO
https://www.jstage.jst.go.jp/article/jjphysiol1950/31/4/31_4_465/_article/-char/ja/

“The hair is there as insulation – to prevent heat from LEAVING the body. Air is trapped in between the hairs and that insulates as it prevents heat from leaving the body and cold air from reaching the skin. So, the more hair – the less chance of heat leaving the body surface……unless it’s windy or the dog is moving around, and the coat is well-kept – as the heat then can escape when the hair is moving. But it’s only a certain amount of heat that can escape and the longer/thicker the coat is, the less effect we have from the hair movement. This is why it is important to keep a long-haired dog well-brushed and to remove excess undercoat if we are going to keep it longhaired.”

However, a thick insulating pelage is a disadvantage in situations where energy supply is unlimited and expenditure is constrained by capacity to dissipate body heat. This is because the pelage insulation becomes the primary constraint on heat loss.

Maximal heat dissipation capacity and hyperthermia risk: Neglected key factors in the ecology of endotherms
Article in Journal of Animal Ecology · April 2010 John Speakman ,Elzbieta Krol
https://www.researchgate.net/publication/44574615_Maximal_heat_dissipation_capacity_and_hyperthermia_risk_Neglected_key_factors_in_the_ecology_of_endotherms/link/5a6721cfaca2720266b43a31/download

A thick haircoat decreases heat dissipation by adding layers of insulation and limiting effective cutaneous vasodilation

Heatstroke:Thermoregulation,pathophysiology and predisposing factors
C.Hemmelgarn,K.Gannon
http://vetfolio-vetstreet.s3.amazonaws.com/50/39d930bce411e28e71005056ad4736/file/PV2013_Hemmelgarn1_CE.pdf

Clipping the coat short decreases its insulating abilities by 50%   according to a scientific article written in 2011 (  Predicted thermal responses of the military working dog  (MWD) to chemical, biological, radiological, nuclear  (CBRN)protective kennel enclosure by Larry G. Berglund, Ph.D.Miyo Yokota, Ph.D.William R. Santee, Ph.D.Thomas L. Endrusick, B.S.Adam W. Potter, B.A.MAJ Scott J. Goldman, V.M.D., Ph.D.Reed W. Hoyt, Ph.D.
https://www.researchgate.net/publication/279517419_Predicted_Thermal_Responses_of_
Military_Working_Dog_MWD_to_Chemical_Biological_Radiological_Nuclear_
CBRN_Protective_Kennel_Enclosure )

A huge amount of studies on cattle, sheep, alpacas, and horses show that clipping the coat short reduces the heat stress in the body. I have listed a few here :

Hair coat characteristics in Friesian heifers in the Netherlands and Kenya  by  H.Veenman

https://www.proquest.com/openview/df176da79a3b42df7f55cd4aca470e82/1?pq-origsite=gscholar&cbl=2026366&diss=y

The effect of clipping the coat on various reactions of calves to heat. By W.Biancahttps://www.cambridge.org/core/journals/journal-of-agricultural-science/article/abs/effect-of-clipping-the-coat-on-various-reactions-of-calves-to-heat/305C548254DE41EF35E5FB380A41887C

Effects of seasonal changes and shearing on thermoregulation, blood constituents and semen characteristics of desert rams  by Mohammed Suahir , M Abdelatif Abdallahttps://europepmc.org/article/med/24517003

The effect of coat clipping on thermoregulation during intense exercise in trotters K. Morgan*, P. Funkquist† and G. Nyman
https://beva.onlinelibrary.wiley.com/doi/abs/10.1111/j.2042-3306.2002.tb05484.x

Seasonal Changes in Heat Balance of Dogs Acclimatized to Outdoor Climate
Yasuyuki SUGANO
https://www.jstage.jst.go.jp/article/jjphysiol1950/31/4/31_4_465/_article/-char/ja/

How does the heat move within the coat?

“This is when things get complicated and this is where the misunderstanding occurred that created the myth of the heat insulating coat.

The hair does insulate against heat -but only against instant heating of the skin -it doesn’t prevent heat from getting into the coat -it only prolongs the time it takes for the heat to get in there. And once it’s there it’s very hard for the dog to dissipate it.

 I will cite a great example from Dr David Marlin -a UK specialist on thermoregulation in mammals –

‘If we take 2 dead dogs, one is short-coated and one is long-coated and put them in the freezer until they are deep-frozen. Then bring them out into a warm day and let them lay there to defrost- the longhaired dog will take longer to defrost thanks to the coat insulating properties

BUT
Live dogs produce heat 24/7 and that heat needs to be able to dissipate or the dog will overheat.  This is the issue with the long /thick coat -it prevents the heat from leaving the body “
( https://www.facebook.com/photo.php?fbid=550815746649470&set=pb.100051631481906.-2207520000..&type=3)

Heat radiates from the skin and heats the air inside the coat. That warm air is slowly heating the air layers further out in the coat until it reaches the surface of the coat. This is because heat is always travelling from warm areas to cold areas. Once it meets the environmental air the transfer will stop.

But if the temperature on the surface of the coat is higher than inside the coat -the same transfer will now happen but in the reversed way.
The warm air on the surface of the coat will heat the air at the inner layer of the coat and heat will now be transferred down into the coat instead.
This transfer stops once the temperature is even throughout the coat.

A prime example of that “reversed” transfer of heat is when you have a dog that lays on a heating pad during surgery.
(When dogs are under anaesthetic, their thermoregulating system is compromised. You, therefore, need to keep them warm during the procedure.)
The danger is though that the heat from the heat pad will be transferred down to the skin and cause thermal burns.

Another factor that you must include is that if the sun is shining, the sun’s radiation will heat the coated surface and that heat will later be transported down into the coat and heat the air inside the coat through heat transfer. 

The isolating air layer at the skin that the undercoat creates will delay the direct heating of the skin -but it will eventually happen.
( ” The microclimate of the canine coat, the effects of heating on the coat and skin temperature ”  https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-3164.1997.d01-12.x  )

( you can read more about the laws of heat  transfer on Wikipedia –  https://en.wikipedia.org/wiki/Heat_transfer  

You can read more on how it works specifically in a coat in my post A deeper look into the role of the coat in the dog’s thermal regulation – https://theeducatedgroomer.com/a-deeper-look-into-the-coats-role-in-the-dogs-thermal-regulation/  )

Recent studies have shown that different hair structures allow for different amounts of heat to be directly transferred down to the skin.
Tight curls only allow for 1/3 compared to straight hair  -giving Lagotto Romagnolo’s an advantage over for example a shih tzu.

(https://www.researchgate.net/publication/340811439_Hair_fiber_morphology_and_
function_at_the_intersection_of_anthropology_physiology_and_engineering )

But they also show that double coats are more effective in preventing the heat to escape out to the surface of the coat . Which is logic as the breeds that we call double coated originates from colder climates.

( Quantifying body surface temperature differences in canine coat types using infrared thermography
Claire J Kwon , Cord M Brundage  Journal of Thermal Biology 2019 May;82:18-22)

‘A typical example of how it works on dogs and in this case we even have it proved that so-called double coated breeds doesn’t ” catch ” cold air to keep them cold 😊  :

C J Chesney did a study in 1996 ” The microclimate of the canine coat, the effects of heating on the coat and skin temperature ”  ( https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-3164.1997.d01-12.x  ) and showed that the temperature inside the coat on a group of  6 border collie type dogs, that was outside playing in a field on a sunny day, had a median temperature of 38 C  ( range between 37-40 C ) when the environmental temperature was 21 C. 

That is 17 C warmer inside the coat than in the environment – even though the dogs were running around outside -so it must have been some movement in the coats that allowed for some heat to dissipate. 

Another part of the study included 7 New Foundland dogs that were kept indoors at a temperature of 23-25 C. The temperature inside the coat was 30 C – again, it’s warmer inside the coat than in the environment. They then let the dogs sit under an infrared lamp for 25 mins -approx. 1 meter from the lamp.  The temperature inside the coat rose to 41C as the surface of the coat got heated. The surface heat got transferred down into the coat and the dogs were negatively affected by the heat increase so they ended the experiment at this point due to the dog’s apparent heat stress.
They could also see that the humidity inside the coat increased -showing that dogs do sweat through the skin.
Other studies have also shown that this happens, but the general conclusion is that it is not a major contribution to heat loss through evaporation.

–    So, you see- a double-coated dog does not have a special coat that catches cold air or is isolated against sun/environmental heat. They will also be affected just like any other dog. 

Here is another study that talks about the fact that it is warmer inside the coat than in the environment: 

“Increasing the air temperature in the model caused the temperature through the depth of the hair coat to also increase. This causes the temperature gradients through the boundary layer to decrease and an associated lowering of the sensible heat loss from the skin surface. For example, at an air temperature of -20°C, the temperature at the hair-air interface was – 16″C, that is, 4°C higher than the air temperature. At 20°C, the temperature at the hair-air interface was higher than the air temperature by 2:C and at 35 C. by I°C (Fig. 2). The sensitivity of the temperature profile to changing ambient temperature and wind speed shows the effectiveness of the hair coat, the boundary layer, as a heat-conserving medium. “ (A MODEL OF SENSIBLE HEAT TRANSFER ACROSS THE BOUNDARY LAYER OF ANIMAL HAIR COAT  K. G. GEBREMEDHIN Agricultural Engineering Department, Cornell University, Ithaca, NY 14853, U.S.A
https://www.sciencedirect.com/science/article/abs/pii/0306456587900155.)

K. G. GEBREMEDHIN also says in his article A model of sensible heat transfer across the boundary layer of animal hair coat from 1986 that: “In the absence of solar radiation, the temperature profile through the depth of the hair coat decreased non-linearly from the skin temperature to the hair-air interface. The temperature at the hair-air interface is higher than the air temperature. “ So, it is warmer inside and on the coat than it is in the surrounding environment.

                      If we want the coat to keep less heat – make the coat shorter

---

The benefit of hair

The coat is on the other hand important to protect the skin from damage and it protects the dog from the elements.

You don’t need a lot of hair to protect the skin if your dog is an average pet dog – only a short layer will do the job – look at all the short-haired breeds.  Your indoor dog will be protected from the elements by your house. Use common sense and leave a short protective layer – don’t scalp the dog down to the skin.

     

But it’s an important factor if you have a working dog – a dog that is exposed to strong sun radiation/ harsh weather/bramble/bushes and maybe even attacks from other animals.  They do need a thicker layer to protect than a pet dog. 

And this is where it gets complicated -again…….

One key heating factor is as I mentioned before the radiation from the sun –

We know that dark colours absorb more heat from solar radiation than light colours. You know yourself the burning feeling on your legs if you wear black jeans on a sunny day – this is why summer clothes have light colours 😉

If you put a blanket over your legs to prevent the radiation from the sun to reach the black fabric it feels cooler. But it is going to be warm under the blanket after a while as it now prevents the heat from leaving your body.

It works in the same way with the dog’s coat -A short dark coat will allow the solar radiation to heat the surface much faster than a longer light-coloured coat.

The surface will be kept cooler on the dog with the longer light-coloured coat – but the radiation will eventually heat the surface on this dog as well.

But -once the sun radiation disappears the short black coat will allow the dog to cool down quickly as the heat from the body can disappear thru the short coat quicker than on a dog with long hair.

The same goes for reflective hair – shiny hair will help in reflecting the solar radiation away from the surface ( just like the reflective sheets that you can put on a window )  and therefore prevent heating of the surface. But  – Radiation can penetrate deeper into a white coat than into a black one (because it keeps being reflected), so some of it ends up being reflected onto the skin. With a dark coat, since the part that heats up stays closer to the surface, it can be removed more quickly by wind. With enough wind, a black-haired animal will gain less heat from radiation than a white-haired one.

But  – if we neuter the dog the structure of the hair changes and it usually goes duller/less shiny ( and we get more wool as well )  It’s the change in the hormones that affect the coat and alters the coat growth cycle so that the undercoat grows longer( Spaying-induced coat changes: the role of gonadotropins, GnRH and GnRH treatment on the hair cycle of female dogs  Iris Margaret Reichler*, Monika Welle†, Christine Eckrich*, Ursula Sattler†, Andrea Barth*, Madeleine Hubler*, Claudia S. NettMettler‡, Wolfgang Jöchle§ and Susi Arnold. )      And we then lose the shiny thin coat and get a dull thick coat instead that reflects less sun and insulates more 

Lots of breeds have been created to have fewer guard hairs and more wool -there are then very few shiny guard hairs left to reflect the sun radiation (poodles and bichons are typical breeds)

Suppose you clip a golden retriever and leave 1 cm of hair and do the same on a poodle. In that case, they will have exactly the same negative effects of the clipping regarding the ability to reflect solar radiation AND protection from the environment. It’s no difference between the breeds.

The other external heating factor is the environmental temperature.

Maximal heat dissipation capacity will also be dependent on the difference between the body temperature and the environmental temperature. Consequently, animals in colder environments will be able to lose more heat.

Maximal heat dissipation capacity and hyperthermia risk: Neglected key factors in the ecology of endotherms
Article in Journal of Animal Ecology · April 2010
https://www.researchgate.net/publication/44574615_Maximal_heat_dissipation_capacity_and_hyperthermia_risk_Neglected_key_factors_in_the_ecology_of_endotherms/link/5a6721cfaca2720266b43a31/download

Lots of studies have been done on animals with the same thermal regulation as dogs and they all conclude that –

“Animals that live in environments where the temperature changes throughout the seasons get a long thick coat during the winter and a much thinner and shorter coat during the warm season. “

So it is obvious that a shorter thinner coat is what nature aims at to keep the animal cooler.

Dogs do adapt to the environment – if they spend a long time in a hot environment the body gets used to it and the thermal regulating process starts at a higher body temperature. But it takes time for the body to do this adaptation. It takes between 20 days to around 2 months for the body to adapt to the new climate.  

This makes it hard for dogs that live in countries like Sweden or UK where the hot weather is only present for a short period and usually arrives suddenly without a chance for the dog to get used to it.
We can see the same thing happening with dogs that move from a warm climate to a cold climate. They will after a while get a thicker coat -but will suffer from the cold in the beginning.

If the surrounding temperature is high but there is no direct radiation – like on a cloudy day or when you are in a car/indoors  – then the coat length/thickness is contributing factor to the ability to keep cool – the longer and thicker the coat is – the harder it is for the dog to keep cool as the heat radiating from the body won’t leave the coat and it heats the dog. 

Studies show that animals with shorter thinner coats deal better with heat than those that have long thick coats if there is very little wind that helps the heat from leaving the air that is trapped inside the coat.
(Effective thermal conductivity of the hair coat of Holstein cows in a tropical environment Alex Sandro Campos Maia2, Roberto Gomes da Silva3, João Batista Freire de Souza Junior2, Rosiane Batista da Silva2, Hérica Girlane Tertulino Domingos
https://www.scielo.br/j/rbz/a/rmg5nCy49SQxCNVDvgBQS4G/abstract/?lang=en)

 
Scientific literature concludes time after time that long thick coats add to the risk of overheating, clipping the coat shorter improves the heat loss from the body and keeps them cooler

Here is a list of several scientific papers that conclude that it’s not beneficial for dogs to have a lot of hair if you want to keep them cool :

“Predisposing factors for heatstroke
-thick haircoat “
ShortTechnical Report on Thermoregulation in Dogs and the Pathophysiology of Hyperthermia Jerilee A. Zezula, D.V.M
http://neacha.org/resources/Short%20Technical%20Report.pdf

“Predisposing Factors for Heatstroke
– thick haircoat “
Heatstroke – thermoregulation, pathophysiology and predisposing factors  Carey Hemmelgarn DVM ChristI Gannon DVM  DacVecc
https://www.vetfolio.com/learn/article/heatstroke-thermoregulation-pathophysiology-and-predisposing-factors

“Factors that inhibit heat dissipation:
Thick, dense coat – increased insulating effect“
Hyperthermia and Heatstroke in the Canine
Lori E. Gordon, DVM
http://usarveterinarygroup.org/usarvet/wp-content/uploads/2016/08/Hyperthermia-and-Heatstroke-in-the-Canine.pdf

“Well-insulated breeds with thick fur and fat may struggle to maintain a normal body temperature,
especially during hot summer days and in a warm ambient environment.“
Hyperthermia during anaesthesia
Author : Clara Rigotti, Marieke De Vries 2010
https://www.vettimes.co.uk/app/uploads/wp-post-to-pdf-enhanced-cache/1/hyperthermia-during-anaesthesia.pdf

“Well-insulated breeds, such as Chow Chows and St. Bernards, may struggle to maintain normal core body temperature, making them more prone to hyperthermia, especially in a warm, stressful environment”
Hypothermia in a chow chow under general anaesthetic
H.Jones, K.Robson ,2022
https://bvajournals.onlinelibrary.wiley.com/doi/full/10.1002/vrc2.423

“Predisposing factors that decrease heat dissipation:  
Hair coat – Thicker coats decrease radiation and convection“

Heatstroke in small animal medicine: a clinical practice review
Scott I. Johnson, DVM, Maureen McMichael, DVM, DACVECC and George White, DVM
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1476-4431.2006.00191.x


“Another group of dogs needing special consideration for temperature ranges are those with extremes in coat type, both those with particularly thick coats, such as Siberian Huskies, and those with thin to absent coats, such as Chinese Crested dogs. Thicker coats decrease heat loss from the skin (Johnson et al., 2006). Without proper attention, such dogs may face thermal distress at higher temperatures than might be acceptable for other dogs”
Temperature requirements for dogs
Mary Jordan, Amy E. Bauer, Judith L. Stella, Candace Croney
Department of Comparative Pathobiology, College of Veterinary Medicine
https://www.extension.purdue.edu/extmedia/va/va-16-w.pdf

However, we have a situation where it doesn’t matter how long or short the coat is, that is when the environmental temperature exceeds 38C/101F. At this point, there won’t be any difference if the coat is long or short, as the environmental temperature will be higher than the body temperature and no chilling of the skin will be possible and no heat transfer from the body will occur. As the inner and outer temperature will be the same -no transfer of heat will happen in any direction.
The dog is now solely relying on panting for heat reduction and that causes stress on the body. Excessive panting is hard work and if you remember what we said before about muscle work creating more inner heat, you can imagine the outcome. It turns into a vicious circle and the dog will be in trouble and need help from us to keep cool.
We can for example wet it down to the skin as the evaporation of the water will chill the skin and help with the heat loss.

Are there any negative effects of clipping the coat short?

Is there a loss of protection from the elements?

The guard hairs do have a purpose – ON EVERY BREED – not just on the double-coated ones. That is why we for example prefer to hand strip wire-haired breeds as the wire guard hairs protect better than the soft clipped coat.
They will prevent the undercoat from being wet/dirty and they protect the skin if the dog is attacked by predators.

Any breed that gets clipped/has its guard hairs removed will be exposed to the elements in one way or another. So-called double-coated breeds won’t suffer more than a Chinese crested from being exposed to the elements – the “suffering” is equal.

But we must also acknowledge in this discussion that it is a huge difference between a pet dog and a working dog that lives outdoor 24/7. A pet dog will have protection from the elements as it lives indoors and we can put a jacket on it when it rains.
So the loss of the guard hairs won’t matter that much to them compared to a wild dog or a dog that lives outdoors 24/7 all year round.
 And we have a lot of breeds that naturally don’t have guard hairs that cover the undercoat and they still survive – look at poodles and bichons for example.


We must again remember that it is not beneficial to shave the dog naked if you want to clip it short for the summer -regardless of breed. Leave a bit of hair as protection for the skin and you don’t have to worry about the dog being without protection from the elements. And it is no different if it’s a poodle or a golden retriever.

Risk of sunburn?

A common argument against clipping is ”  The poor dog will get skin cancer if you clip it “

Any dog that gets scalped with a 30 blade in reverse will suffer sunburn if we don’t allow the skin to gradually get used to the sun and get a natural pigmentation to protect it.
But there are very few so-called double-coated dogs that get clipped that short …. there is, on the other hand, a lot of show poodles get done with that blade every year all over the world and no one says anything about it… And there are no indications that they have an increased ratio of skin cancer.

Solar dermatitis is not uncommon in dogs – and it’s the white-haired and non-pigmented skin of short-coated breeds such as pit bull terriers, Staffordshire bull terriers, bull terriers, boxers, Dalmatians, and similar that gets affected but any dog with white or lightly pigmented hair and skin is at risk.
(Diagnosis and treatment of solar dermatitis in dogs  2007   Kimberly S. Coyner, DVM, DACVD   https://www.dvm360.com/view/diagnosis-and-treatment-solar-dermatitis-dogs  )

No written papers that I read said anything about clipped double-coated breeds being of extra high risk  – they all mention naturally short-haired breeds – both for skin cancer and solar dermatitis.
But if you shave a golden retriever with a 30 blade in the middle of the summer -their skin will of course be as sensitive as the non-pigmented skin on a bullterrier.

It’s important to use common sense if you clip a dog short for the summer! Leave at least 1 cm of hair to protect the skin. It won’t do a huge difference for the dog from a heat dissipation point of view if you clip it with a 7F or a 4F – so leave some protection.

A dog can get severe burns from the sun if they are exposed to strong UV sunlight and high temperatures while in a high attitude for a prolonged time – its more common in short-haired dogs with a dark coat ( as the dark colour attracts the heat from the sun ) – but you can see it dogs with lighter coats as well.
( Dorsal thermal necrosis in dogs -a retrospective analysis of 16 cases in southwestern USA 2009-2016  Stephanne L Swartz, Anthea E.Schick, Thomas P Lewis, Diana Loeffler
https://onlinelibrary.wiley.com/doi/abs/10.1111/vde.12519 )

But this means that all breeds with short dark hair are at risk – not just a clipped collie.  So every owner needs to take that into consideration if they live in a high-risk area – regardless of breed. And again – dont skin the dog….. leave a bit of hair to protect the skin.

Have a look at the pictures below –

Here are 5 dogs done with the same blade – a 7F

               According to the No side –one of them will suffer – the rest will be ok –“ as they have a different coat and thermoregulation. “……..

                                                Can you spot the one that will suffer?  

Probably not – as all of them will be wet when it rains and all of them will have an increased risk of getting cuts when running thru bramble –and a couple of them will have an increased risk of changes in the coat texture due to the clipping.
But they ALL regulate their body temperature in the same way – there is not a different thermoregulation system for double-coated breeds.

But what about the destroyed coats if you clip a double-coated breed?

This is where the problem arises when we talk about clipping dogs short for the summer.
Some breeds can get changes in their coat if we clip them and that can be an issue later on as it can take a long time before it grows back to the normal look. It can be as long as several years before its back to normal in the breeds with a “nordic type” of coat ( huskies, Samoyeds and similar )
We must therefore weigh the pros and cons before deciding if we should clip them.
And by clipping, I don’t mean scalp the dog with a 30 blade, clipping just means making it shorter

Why can the coat change?

( more info can be found in the book  Muller and Kirks Small Animal Dermatology )

“The coat is there to protect the skin from damage from the environment and to help the dog to keep its core temperature regardless of the environmental temperature “

The term COAT describes the mass of hair that covers the dog  – and the term HAIR is the individual hairs that form the coat.

There are primarily two types of hairs that make up the coat – guard hairs and wool/undercoat. (some dogs have 2 different types of undercoats) Dogs also have tactile hairs  – what we usually call whiskers

The guard hairs can be of different textures depending on the breed of the dog. And the dog can have different types of guard hairs on different body parts – as collies for example that have short guard hairs on their face and the part of the legs and then long guard hairs on the body. The wool is shorter and softer in texture and mostly looks the same all over the body.

Every breed is in fact double-coated – all dogs have a shorter woolly undercoat to keep them warm and stronger longer guard hairs that are aimed to protect the undercoat from being wet and dirty. But thru selective breeding, we have changed the coat in some breeds, and it can nowadays be hard to see the difference between the wool and the guard hairs – as in poodles for example. We have also aimed for less undercoat in some breeds, and they can for the naked eye appear as single-coated – Yorkies is one of them.

The breeds that traditionally are classed as “double-coated” in grooming terminology are the ones that have longer wool and longer guard hairs – but there is still a clear definition between the wool and guard hair and the hair lays down. They are seldom styled – most of them are left natural and just get a tidy up. A typical example is Golden Retriever, Tibetan spaniels, and New Foundland. Included in this group are also the “Nordic type” breeds  – dogs that have a spitz-type coat with thick short wool and longer stronger guard hairs and both the wool and guard hairs are standing out from the body rather than laying down. The naming Nordic type comes from the fact that most of them originate from cold climates – Siberian Husky, Norwegian elkhound and Samoyed are some of them.

Spaniels, terriers, and schnauzers also have a typical “ double coat” that works just like nature intended – strong shiny guard hairs that protect the short thick wool that keeps them warm – but they are not for some strange reason included in the term “ double-coated” in the discussions.

As mentioned before – all dogs have a double coat – wool and guard hairs. They share the same hair follicle – but have two separate growth cycles. The cycles are run by several factors like hormones, temperature, daylight, nutrition, stress, and genetics

There are 5 stages in the growth cycle

Anagen or Growth Phase

The anagen phase is the first phase of new hair growth. Dogs that do not tend to shed heavily have a longer anagen phase. Dogs that continuously shed have shorter anagen phases. The amount of time the hair follicle stays in the anagen phase is genetically predetermined.  Poodles for example spend almost 98% in the anagen state – their coat grows more or less constantly. Other breeds with short hair spend only a short time in this phase.

Catagen or Regressing Phase

The catagen phase is the transition phase. The catagen phase begins when the cell creation signals to stop. Hair stops growing during this phase as the outer root sheath attaches to the hair.

Telogen or Rest Phase

Telogen is a rest period between the catagen and anagen phases. This period varies depending on the type of coat the dog has – in most breeds this is the longest period in the cycle. Breeds with a “Nordic” type of coat – as Huskies, Elkhounds can spend several years in this phase. This is nature’s way of using nutrition/energy in a good way – in a cold climate, you need the energy to keep you warm – not to grow a coat.

Exogen or Shedding Phase

The final phase, exogen, is the shedding phase. This phase occurs when the hair falls out and the follicle moves back into the anagen phase. The length of this phase depends on the season.

A new phase has lately been introduced when we talk about coat growth phases – ‘‘kenogen’’: It applies to hair follicles that have passed the telogen stage, lost their hair fibre (exogen), and remain empty for a certain time before a new anagen phase is starting.

( The Hair Follicle: A Comparative Review of Canine Hair Follicle Anatomy and Physiology. Monika M. Welle and Dominique J. Wiener ,2016
https://pubmed.ncbi.nlm.nih.gov/27000375/)
And even more recently a 6^th phase has been suggested -zenogen. That is when a hair follicle is in the kenogen stage but it ends up dormant -it never moves on to the anagen stage.
This is what can happen with certain hairless breeds.

The hair follicles are all in different stages all over the dog – some are resting – some are preparing to shed –some shed and some are creating new hair. There is a practical reason for that – creating new hairs demands a lot of nutrition so if all hairs fell out at the same time there would be a huge amount of nutrition needed to create a full coat again – and it is going to be tough to fill that demand. But if some hairs are resting while others are created the nutritional demand will be much lower. ( approx 30% of the nutritional intake goes to the skin and hair – but as this is the less important part of the body organs it gets the leftovers after the heart, lungs, brain, and other organs have had their share )

We would also lose the purpose of the guard hairs if they all fell out at the same time – that would leave the dog without a “weather shield “ and expose the wool to the elements. This does happen when we clip them short ( regardless of breed ! ) -So clipping them short has its downfall – but it also happens when we strip down wire-haired dogs as border terriers and jack russels or clip a shihtzu ……

And remember now that there is one cycle for the guard hairs and one for the undercoat/wool.

As I mentioned above – some breeds guard hairs can be in the resting phase for 4-5 years – while the undercoat usually has a 6-month cycle on most breeds  –they shed and grow new undercoat twice a year as the undercoat is there to keep them warm in the winter and gone in the summer to keep them cool. During spring they shed the thick winter wool and set thinner summertime wool and then in the autumn is time to shed the summer wool and set thicker winter wool again. The shedding of the wool is much more synchronized and usually happens all over at the same time – at least it feels like that when it happens ….
When we clip a so-called double-coated breed there is a risk that the guard hairs won’t grow back for a long time and the dog will look really stupid during that time. It all depends on where in the growth cycle the hair is when we clip the dog.  It can grow back just fine but in the worst-case scenario, it can be at the start of the resting phase, and it will be 2-3 years before all hairs are out in normal length. Or the dog is elderly, and the body decides that nutrition is needed for more important things than hair….
During this time, the undercoat will now be the main protection for the skin and it can turn into a more wire structure and end up being hard to keep mat free.

A lot of elderly dogs also suffer from medical problems and that will also affect the growth as the body needs the nutrition to battle the sickness – not to create hair.

It can sometimes be an underlying medical problem that suddenly gets visual when you clip the hair. There are medical conditions that cause the hair follicles to go into a permanent resting state.
You won’t see it until you clip the dog as the hair isn’t growing – but it’s not the actual clipping that caused it – it just made it visible.

The body can also decide to put the hair follicles in a permanent resting phase when we clip them short. This is most common in the ” Nordic type” of breeds – but it sometimes occurs in other breeds as well.  The cause of this is still not known – one of the theories is that the cooling of the skin when the hair is gone gives a signal to the body to reduce the blood flow to the skin to keep the core heat and that affects the hair follicles growth cycle-moving them all to the telogen stage. Another theory is that hormones are disrupting the growth cycle.
( A Colour Handbook of Skin Diseases of the Dog and Cat UK Version, Second Edition, Patrick J. McKeever, Tim Nuttall, Richard G. Harvey)

So YES- you might “destroy” the coat by clipping it short.
Or to be correct – in most cases, you destroy the look of the dog. The coat isn’t destroyed as it’s just following its natural cycle – but the dog will look crap during that time.

If it’s a “Nordic” type of coat -then it can take several years before it’s back to normal again, and the coat maintenance during that time can be challenging.
 There is also a risk that underlying medical problems suddenly get visual or that the hair follicle goes into a permanent resting state and the hair never grows back again.  This is why it’s so important to inform the owner of how the coat growth cycle works and make them sign a paper that they are aware of what can happen if you as a groomer are going to clip this type of coat.

We also must make sure that we do a thorough de-shedding before we clip them, which will remove as much of the hairs that are ready to be shed as possible – making sure that the hair follicles are now moving on to the anagen stage and increasing the possibility of proper regrowth.

( And remember that this can happen to other breeds besides the ones we call “double-coated” –  but the problem is more common in them. )

“I have heard that that the undercoat gets thicker when you clip them – so that will increase the risk of heatstroke rather than preventing it !! “
This is a claim that pops up during discussions – but I have so far never seen any evidence for it. I haven’t seen it on dogs I have done, and the groomers I have discussed this with haven’t seen it either.
And I can’t find any mention of it in scientific literature.

I am however open to corrections if any of my readers have any scientific papers/books that mention it :)-please comment or send me an email if you have anything and I add it to the text.

I think it is probably the fact that we never really see how much undercoat they have when the guard hairs cover it, that makes people think it is extra thick once they see it growing out without the guard hairs.
The undercoat that grows out before the guard hairs can be challenging to deal with -as it has a tendency to mat up if the dog is neutered. So it is important to wash and condition it on a regular basis to keep it in top condition. And do regular de-shedding treatments -just like we do when they have a “full coat”, as that helps to maintain healthy skin and coat.

So what shall I do ??

First and foremost – we must remember that the heat/sun radiation/wind/humidity is different in different parts of the world. What can be completely ok in northern Sweden might not work in Arizona. Use common sense!

And acknowledge that different individuals have different tolerance to heat. My dogs are a prime example of that.
My poodle gets affected by the heat once his coat is longer than 3 cm-he is even hot in normal indoor temperatures. Once I clip him shorter I have a new dog 🙂 He is like a pup again.
My fox terrier on the other hand can lay in the sun and roast for ages ….and she would sleep on top of my stove when I have a fire going if I allowed her.

Yes –the dog might end up looking stupid for years in the worst-case scenario if it’s a double coated breed- but it won’t die from heat stroke because you clip it. But it might on the other hand suffer from severe heat stress if you don’t clip it.

Look at the dog – if it is affected by the heat -then it needs a shorter coat.

” But I have heard that the dog can suffer from a heatstroke if you clip it as you remove the insulation from the heat ?”
If there was an increased risk of heat stroke due to the clipping there would be lots of suffering dogs at the vet clinics and warnings in veterinary literature – dogs are clipped daily all over the world and we still don’t see any warnings in the scientific literature.

I did a search on Google scholar and didn’t get a single match when searching for “heatstroke clipped dogs “  – I did on the other hand get a lot of articles that said that one way of preventing heatstroke is to clip the coat short as a thick coat increases the risk of heatstroke ………
( see previously posted links :  Heatstroke: thermoregulation, pathophysiology, and predisposing factors, Carey Hemmelgarn 1, Kristi Gannon  Pathophysiology and pathological findings of heatstroke in dogs   Mariarita Romanucci, Leonardo Della Salda )

And Yes – there won’t be a difference for some dogs if you clip it short or just wash it and remove all the dead undercoat  – if it’s a light-coated dog like a long-haired chihuahua for example and the dog will look so much nicer in its natural style.

But a fat neutered long-haired chihuahua with a thick woolly coat like a Leonberger will feel much cooler in a short trim. But use common sense and don’t scalp it- leave 1 cm so that there is a layer of protection for the skin.

Or shorten the coat on the body a little bit and do a proper de-shed treatment.  Clip it short on the stomach to open a window for the heat to dissipate -the coat on the stomach has fewer guard hairs and they have a faster growth rate than the ones on the back, so we don’t see the coat damage there.

If it’s a working dog that is living outside 24/7 – like a dog that lives with a herd of livestock – they would need a long coat to be protected from the elements/predators and the solar radiation. Most of those breeds are from areas where it is warm but windy – so you will have natural convection that moves the coat and releases the heat trapped inside. That dog would do better with a de shedd and clipping a ” window “on the stomach.
These are dogs that don’t do explosive movements -they rest together with the herd and can choose to lay in the shadow – so they don’t create a lot of extra inner heat.

On the other hand – working dogs that do a lot of explosive work in hot environments – like army dogs, agility dogs, and Schutzhund –benefit from being clipped shorter.
They do intense prolonged work and that will create a lot of extra inner heat that they need to be able to dissipate.

And for other dogs, the difference can be huge if you clip it shorter. Especially if the dog is overweight AND old as the fat acts as extra insulation and prevents the heat from radiating from the body and the old age makes their thermal system less effective.

Dogs with a thick coat that doesn’t get thinner due to brushing –  Like a thick-coated poodle or a neutered Newfoundland for example – will definitely get relief from the heat if they are clipped shorter.  The thick coats won’t release any heat as it’s not moving in the wind like a thin collie coat and the guard hairs are either very few or dull due to neutering and therefore don’t reflect the sun radiation – so they won’t be missed if the dog is clipped short.

    So I am sorry to say –  the conclusion after all this reading is- there is no ” one size fits all ” answer

Yes – a shorter coat will make the dog feel cooler – but we must also weigh in the other factor of the risk of coat damage in some breeds.

You must look at each individual dog and make a decision based on this dog’s circumstances:

If it’s a breed where the coat has a continuous re-growth -like a poodle, then it’s a no-brainer – clip the dog if you/the owner feels it’s struggling with the heat. A shorter coat will allow it to dissipate heat better.

But don’t scalp it-leave a bit of hair to protect the skin.

If it’s a “double-coated ” breed – then it gets a bit more complicated.
Is the owner prepared to have a dog that might look crap when the coat grows out due to the uneven regrowth? – if so – clip it if that is what the owner wants. Just make sure they sign a paper that you have informed them.

Do you live in Ireland where we have 1 week of “heat” per year? Maybe it’s not worth the risk of the uneven regrowth on a double-coated breed for that single week. It can maybe be managed by a good de-shedding treatment, clipping the stomach short and keeping the dog in the shade and wetting it down if it appears hot.
But if the dog is old, neutered, has health issues or is overweight- the benefits will outweigh the risk of crappy regrowth.

Is it a collie or a husky?
Collies/retriever coats usually tolerate being clipped once a year for the summer without damage so I wouldn’t worry that much.

The nordic type of coats can on the other hand look horrible for several years if you clip them -is it worth that risk? Will the benefit weigh up the risk? Look at the individual dog and make a decision based on that dog’s circumstances.
– if the dog struggles with the heat -I personally would rather have a dog with a crappy coat than a dead dog/or one with permanent damage to its body due to heat stress …….

Is it a dog that is constantly wet as it swims every day and therefore at a higher risk of hot spots- a shorter coat will prevent suffering and unnecessary medication.

If the dog is elderly/overweight/have health issues -removing hair will make life easier for it.
If the dog lives in a climate with hot weather 10 months per year -then you will have a real benefit from it. If the dog on the other hand lives in an environment with 2 weeks of warm weather and is not neutered and doesn’t carry any extra weight -then other actions might be taken to keep the dog comfortable and we can avoid the risk of the uneven regrowth.

And remember – a double-coated breed won’t suffer more than a poodle from being clipped and they get equally affected by the heat as any other breed. They can´t ” catch cold air” with the undercoat.
If it’s 30C outside -there is no cold air to “catch”.

Educate yourself and then make a decision based on facts – not based on random memes/posts on Facebook.

If you want to read more about the role of the coat in the thermoregulation process – go to my post about that subject; A deeper look into the coat’s role in the dog’s thermal regulation .