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Writer's pictureAislinn Evans-Wilday

Why Do Dogs Die In Hot Cars?

Today's blog post is a hot topic, if you'll excuse the pun.


I have no doubt that there will be some people who got as far as that line and thought nope! before immediately leaving again and that's fine, this space isn't for them, it's for you and me.


So why do I want to speak to you about this undoubtedly unpleasant topic today? Well, it's terribly easy for me to assume that all dog owners know this, but every summer, I am surprised by the number of my clients who still ask me if I will be walking their dog on a day like today when it is currently 30°c.


That's not entirely fair actually. Asking me if I will be doing any walks on these hot days is a perfectly reasonable question as I will quite often do one early walk on these days, before it gets too hot, in the woods where it's shaded and a good 3-4 degrees cooler than the ambient temperature and where the dogs can splash around in the stream. What actually surprises me is the number of clients who are surprised when I tell them that I will be walking their dog earlier than usual if at all, and those who genuinely don't know the risks of exposing your dog to the summer heat.


But, you don't know what you don't know and it's not fair or sensible of me to assume that everyone is as aware of the risks as me. After all, it is my job as a professional dog walker to know a thing or two about canine care and I also like to think of it as my job to educate those around me about these things as I see fit and this my friends, is one of those times.


a happy-looking boxer dog, panting on a sunny day

Why DO dogs die in hot cars?

When I was at university, we had a lecture on why dogs die in hot cars. It wasn't named as such, but it was the gist of the lesson and it has stuck with me to this day. As a relatively new puppy owner at the time, I was learning anything and everything about dogs and fortunately for me, a lot of the anatomy and physiology we learned in BSc Equine Sports Science was taught from the angle of being compared to the anatomy and physiology of our canine companions. It's not all that surprising now that I went on to start a dog walking business...


There is one key fact you need to know about dogs and how they regulate their body temperature and it is this: DOGS CANNOT SWEAT.


You probably already know this but what you probably don't know is the implication this has on their bodies in high temperatures. It's time for a science lesson!


 

Ok so, when an animal's body gets hot (be that human, horse or dog), the internal temperature rises. You've heard of homeostasis right? It's the body's ability to regulate and keep things the same, so when the body gets too hot, it cools itself down and vice versa.


In order to cool itself down, heat is transferred from the organs (got to keep them cool!), to the blood, to the skin and mucus membranes (in the mouth). At the skin level, hot blood meets slightly cooler skin, sweat forms and is then carried away by the even cooler air by the process of evaporation.


Panting works in almost the same way as sweating and it is evaporation of water from inside the mouth, the tongue, the nasal passages that cools the dog down.


The big difference between sweating and panting is surface area. A body that can sweat through the skin has a very large surface area to evaporate water (sweat) from whereas panting is limited to the mouth.


a well-kept horse, sweating after exercise

This in itself means that dogs have a much harder time keeping cool when the weather is hot but it has deadly ramifications when it comes to hot cars.


This is because of the fact that energy cannot be destroyed only transferred, and the energy in this case is heat. Heat always transfers from areas of high concentration to areas of low concentration, for example; when you add something hot to something cold (like plunging a hot skewer into cold water), the heat travels from the hot area to the cold area until they become equal temperatures (or as near as possible).


What this means for our panting dogs is that as long as the temperature outside of the mouth and tongue is cooler than the temperature of the body (which should be 38-39°c), heat will leave the body via the mouth and tongue and travel to the cooler area. That is how panting works.


The problem with cars and why dogs die inside of them is that the temperature inside the car becomes higher than the dogs body temperature and as we just learned, heat travels from an area of high concentration (the hot air of the car) to areas of low concentration (the dogs body) until it equals out. When the ambient temperature is higher than body temperature, that heat is going to try and get into that body.


This is where it gets really nasty and if you've heard enough to understand that dogs can't keep themselves cool in hot cars then do yourself a favour and don't read any further.

a cocker spaniel with it's head out of a car window on a sunny day

As the cells of the body get hotter and hotter, they begin to vibrate. That's what cells do when you heat them up. Again, energy can't be destroyed, only transferred, and heat energy becomes movement (kinetic energy). Ironically, movement also creates more heat so you end up with a vicious cycle of hot cells vibrating faster creating even hotter cells. With this increased energy, the cells become damaged as their structures change irreversibly and the dogs quite literally cook.


I told you it was horrible.


The danger with cars is that the temperature inside of them rises so quickly on a hot day and they become literal ovens for the dogs trapped inside of them. But the dangers aren't limited to cars. As we've discussed, the body is able to cool itself down when the ambient temperature is below body temperature and while it has never reached 38°c in the UK, temperatures above our classic room temperature still pose a risk to our furry friends because of that one key fact from before: DOGS CAN'T SWEAT.


A human body is far better equipped at cooling itself down because of the large surface area of skin we have available to us for sweat evaporation. Dogs can sweat a tiny amount through their paws but the rest of their cooling comes entirely from panting.


a small, white, curly haired dog, looking knowingly at the camera on a sunny day

So how do we help them?

There is one other method by which our furry friends can cool themselves down and that is by physically moving themselves to somewhere cool. We're all familiar with dogs lying on cool tile floors when it's hot and jumping into streams and rivers.


This mechanical means of cooling down works in almost the opposite way of sweating and panting. When the blood carries heat from the organs to the surface of the skin or the mucus membranes, it is cooled slightly when it reaches the skin and the lungs thanks to the cool air on the skin and the cool air breathed into the lungs. The cooler the skin is, the cooler that blood becomes and that cooled blood is then carried back to the organs to cool them down.


However, there are risks here too.


If the skin is cooled too rapidly, then the blood vessels constrict, making them smaller and therefore making it harder for heat to transfer because of the smaller surface area. This is why you should never use a hose or bucket of water to cool down a dog that you think might be struggling from heat stroke. Water that is too cold will cause the blood vessels to constrict, making it harder for them to cool down.


You can use tepid water to cool them down slowly but it is far safer to provide a cool room, or shady spot with a cool damp towel and a fan. Hosing down a hot dog will only make them pant more and take them longer overall to cool down.


The other risk associated with walking your dog in high temperatures is the affect that it has on their paws. I like to think that the audience of this blog will already know all of these things but in case you're new to this dog-owning malarkey; have you ever walked on a hot pavement in the height of summer? If it's too hot to keep your hand there, it's too hot for your dogs paws. Every summer there are numerous cases of dogs going to the vet with burnt paws and it's so avoidable.


The point of this post is not to re-iterate that you shouldn't walk your dog in hot weather, I'm assuming that you already know that, but to instead explain to you why it's dangerous at a scientific level (scientific, but in lay-mans terms). My goal here is to educate those of you who know enough to make smart choices around your dog's health and well-being but who are still at the risk of not erring on the side of caution. No dog died through missing a day or two of walks, but multiple dogs die every year because of heatstroke. It's completely avoidable and my hope is that now you know exactly what is going on under the surface of your dog's skin, you're better prepared to make good choices about your walks this summer.

a happy dog cooling down in the sea

Forever paws,

Aislinn 🐾



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