MY HAIRY UNIVERSE

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

Its 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.

But there was no information about the picture – where was it taken? Indoors? Outdoors? Is the sun shining on the dog? Is it hot or cold around the dog?  Is the dog dry or wet? Clean or dirty? Had the dog recently been running around?   Those are all factors that affect the outcome of the picture.

The picture shows how much heat that is radiating FROM the surface of the dog ….. and it will off course be more heat coming from the clipped area than the long-haired one as the coat insulates and KEEPS the heat from slipping away from the dog.  ( read more about thermal images of dogs  in this paper – Mari Vainionpää Thermographic Imaging in Cats and Dogs Usability as a Clinical Method,2014)

It would have looked the same if we took a picture of a boxer with a towel over his shoulders……

So the picture showed that the coat was doing its work properly – it kept the heat from leaving the dog 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.

The important temperature to know is the dog’s core temperature – the temperature INSIDE the dog. That is the temperature that actually shows us how the dog is doing.
The temperature on the outside is irrelevant as that only shows what the temperature is on the surface of the skin and that is depending on the environmental temperature, radiation from the sun, and much more.

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 behavior https://www.facebook.com/DrMelissaStarling/ )

Another interesting fact during the discussions is that all 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 them – 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 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.
And then you will be able to do an educated decision based on proven scientific facts that can be verified rather than pseudoscience and myths.

         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 the NO 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 language so it’s easy to understand even if you don’t have any medical training.

So grab your coffee and start to read – it is going to be a long journey ……

The basics  – A simplified explanation 

( more info can be found in Muller and Kirks Small Animal Dermatology )
The coat is there to protect the skin from damage from the environment and to keep the dog warm.

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.
( Dogs also have tactile hairs  – what we usually call whiskers  )

The guard hairs can be of different texture 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 in their face and on 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.

If we start with the basic – What is a double coat?

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.

Guard hairs on a poodle

Spaniels, terriers, schnauzers all 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.

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 retrievers, Tibetan spaniels, and New Foundlands. Included in this group are the “Nordic type” breeds as well – 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.

Now when we have established what a double coat is – let´s look at how the coat works.

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 4 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 fiber (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 )

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 intakes 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 exposing the wool to the elements. Wich 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 high 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 its 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….

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.

Patchy regrowth of the guard hairs on a collie – you can see how there is mostly wool and then single guard hairs here and there.
This dog is clipped with a 7F roughly 3 times per year – he mostly looks like this when coming in for his groom – but every second year his coat is back to normal. 

Patchy regrowth on a spaniel – this is common in spaniel type of coats ( springer spaniel,cavalier ,cocker spaniel ) when the dog gets older or has a medical condition.
Thyroid problem is a common cause for this type of patchy regrowth. Lack of thyroid hormone delays the start of the growth phase.

Patchy regrowth of wool on a collie – you can see the new guard hairs coming up in the short area.

And it’s sometimes 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.
So there is a risk that the hair never grows back again….

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. 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 the time. But there is 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.

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

So we now know how the hair grows and what’s affecting it – but what about the thermal regulation?
How do dogs keep their body temperature at the right level?

( Read more in Guyton and Hall Textbook of Medical Physiology )

All warm-blooded animals have the same basic thermoregulation system – dogs, cats, hamsters, humans, birds….. the basic is no different. Once you look into 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 in 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 back 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 to 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.

We must also remember that we have changed the breeds thru out the years to please our eyes…..

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 causes changes in the coat growth cycle and changes the    coat. Lots of breeds get twice the amount of undercoat that nature Intended and the undercoat is not shedding in the same way it used to do.

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

In order to maintain a constant body temperature if the environment is warm 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 )

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 tiled flooring for example.

Some heat is also transported from the skin thru 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 actually 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.

How is that done?
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 into 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 more flat 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.

If the dog is fat the radiation will be less effective as the fat doesn’t transport heat well – so the fat will actually 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 first three mechanisms are ineffective, and the animal must rely on so-called evaporative cooling mechanisms: sweating and increased respiration

Evaporation: the process when a fluid is changing to a vapor.  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 condensation occurs when the hot blood 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 by 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.

         So to make it short – at lower environmental temperatures body heat is lost thru radiation in 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

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

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 than 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.
That 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.

     Some of the No-sayers argue and say – the hair insulates FROM the heat as cold air is trapped inside  – but we will have to argue that point…..
Heat is radiating from the body – so it’s warm air that gets trapped inside the coat. And if the environmental temperature is high – where do you get the cold air from? If the air that surrounds the dog is warm – then it will be warm air trapped inside.

“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.)

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 the coat than it is in the surrounding environment.

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. )

Several studies on cattle, sheep, alpacas, and horses show that clipping the coat short reduces the heat stress in the body.
(Hair coat characteristics in Friesian heifers in the Netherlands and Kenya  by  H.Veenman
The effect of clipping the coat on various reactions of calves to heat. By W.Bianca
Effects of seasonal changes and shearing on thermoregulation, blood constituents and semen characteristics of desert rams  by Mohammed Suahir , M Abdelatif Abdalla
The effect of coat clipping on thermoregulation during intense exercise in trotters
K. MORGAN*, P. FUNKQUIST† and G. NYMAN ) )

                      So if we want the coat to insulate less heat  – clip it short

But 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.  And your indoor dog will be protected from the elements by your house.
So 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. 

One key heating factor is the radiation from the sun –

We know that dark colors 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 up the surface much faster than a longer light-colored coat.

So the surface will be kept cooler on the dog with the longer light-colored coat – but the radiation will eventually heat up 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 the 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 actually 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 reflect less sun and insulates more 

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

So if you clip a golden retriever and leave 1 cm of hair and do the same on a poodle – 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 heating factor is the environmental temperature.

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 in order 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.

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 wont leave the coat and it actually heats up 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)

    Scientific literature concludes 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 if the dog is in a hot environment without any or little movement of the hair that allows the heat to leave the coat.

( ShortTechnical Report on Thermoregulation in Dogs and the Pathophysiology of Hyperthermia Jerilee A. Zezula, D.V.M
Heatstroke – thermoregulation, pathophysiology and predisposing factors  Carey Hemmelgarn DVM ChristI Gannon DVM  DacVecc )

“Accordingly, hyperthermia might become a problem in hot, humid areas outside of their original habitat. Several studies showed the beneficial effect of shearing against heat stress. In particular, fertility in males exposed to heat stress may be improved by shearing. Infrared thermography reveals that in shorn animals the heat is radiated across the entire body surface and is not restricted to the thermal windows. ”
Relationships between integumental characteristics and thermoregulation in South American camelids by M. Gerken

So what about protection from the elements – “ if you clip a double-coated breed you expose them to the elements “

Any breed that gets clipped/has their guard hairs removed will be exposed to the elements…..and so are the hairless breeds like Chinese crested and American Hairless terriers. There is no difference …..

So-called double-coated breeds won’t suffer more than a Chinese crested from being exposed to the elements – the suffering is equal.

           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.

And what about skin cancer and sunburn??

Any dog that gets scalped with a 30 blade in reverse will suffer sunburn if we don’t allow the skin to gradually getting used to the sun and get a natural pigmentation to protect. 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 a thing 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 )

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 off course be as sensitive as the non pigmented skin on a bullterrier.

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 )

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.

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.

                                In the end, it is up to personal preferences what you do

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

Yes –the dog might end up looking stupid for years in the worst-case scenario – but it won’t die from heat stroke because you clip it.

If there was an increased risk of heatstroke due to the clipping there would be lots of suffering dogs at the vet clinics and warnings in veterinary literature – dogs are clipped on a daily basis 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 “heat stroke clipped dogs “  – But I did get a lot of articles that said that one way of preventing heatstroke is to clip the coat short………

And Yes – for some dogs there won’t be a difference if you clip it short or just wash it and remove all the dead undercoat  – if it’s 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 longhaired chihuahua with a thick woolly coat like a Leonberger will probably feel much cooler in a short trim. But use common sense and don’t scalp it- leave 0.5-1 cm so that there is a layer of protection for the skin.

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 the long coat to be protected from the elements 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.

On the other hand – working dogs that have shelter from the elements and do a lot of work in hot environments – like army dogs,agility dog,shultzhund – they benefit from being clipped short.
( The effect of coat clipping on thermoregulation during intense exercise in trotters
K. MORGAN*, P. FUNKQUIST† and G. NYMAN )

And for other dogs, the difference will 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 New Foundland 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 doesn’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 …….

You must look at each individual dog and make a decision based on this dog’s circumstances :
Is the owner prepared to have a dog that might look crap when the coat grows out due to the uneven regrowth?
Is it living indoors or outdoors ?
Young – middle-aged -old?
underlying medical conditions?
Fat – normal?
Thin coat – thick coat?
Owners purpose with the dog – working dog? What type of work is it doing?  Pet dog – is it a “living in the garden ” pet – or long walks by the sea dog ( that is constantly wet and therefore at a higher risk of hot spots … )

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