There’s a profound misconception about heatstroke in the UK – and that’s probably because we don’t have heat waves often enough to have to deal with it! Basically, people think that dogs cope with heat the same way that we do. They really, really don’t!


What are the differences between how dogs and humans handle hot weather?

Modern humans evolved in the hot climate of East Africa. Although we’ve modified our bodies a little in the last hundred thousand years or so, we’re still basically adapted for that environment. We’ve lost our body fur, and developed thousands upon thousands of glands in our skin that release salty water when we’re hot – sweat. When this water evaporates, we cool down, fast, within minimal loss of water.

Dogs, on the other hand, are lineal descendants of wolves – arctic animals that evolved to live in the forests and tundra of the far north. They have a thick fur coat to keep them warm (OK, this has been modified in some breeds, but the principle holds!), meaning that they lose heat, only slowly. In addition, they don’t sweat to cool down (because in the arctic winter, a wet coat can be a death sentence). If they do get too hot, they pant, allowing their saliva to evaporate. However, this isn’t very efficient, because the muscular activity of panting generates lots of heat – not as much as they lose, but nevertheless, enough to make it hard for them to stay cool in hot weather. As a result, dogs are also more prone to becoming dehydrated in hot weather than humans (who are remarkably well adapted for hot weather).


What happens to dogs who get too hot?

Overheating will result in heatstroke, if the dog can’t cool themselves down fast enough. This is why they pant and try to find shade – to reduce their body temperature before it becomes dangerously high.


What is heatstroke?

Heatstroke, more or less by definition, is a condition where the body is too hot and cannot lose that heat as fast as it is being generated. The problem is that, like all animals, a dog’s body cells keep functioning because of microscopic molecular machines, called enzymes. Once the temperature goes above a certain limit (roughly 42C), these enzyme machines become “denatured” – they shut down, permanently. This results in cell death. The most vulnerable organs are those deep inside the animal that cannot shut down – especially the brain, the liver, and to a lesser extent the heart. As a result, heatstroke leads to brain damage, liver damage, and then death.


What causes heatstroke in dogs?

There are two types of heatstroke in dogs:

Exertional Heatstroke occurs when the dog is exercising and is internally generating more heat than they can lose – this mainly occurs when your dog does too much in hot weather.

Non-exertional Heatstroke is the alternative – when the environmental temperature is too high and the dog cannot cool themselves down as fast as their temperature is rising. This is the situation we see with dogs in hot cars, or conservatories, or even open gardens with no shade in the midday sun.


What are the symptoms of heatstroke in dogs?

Initially, the dog will pant, often excessively, trying to cool themselves. However, they soon become dehydrated and as a result, their saliva becomes thicker and thicker – this is visible as drool or slobber.

At this point, their ability to lose heat is severely compromised, and their internal organs start to fail. Initially, their brain malfunctions, causing drowsiness, disorientation, wobbliness, or even seizures. They are then likely to collapse, and may die directly of multi-organ failure, or of dehydration and shock.


What first aid can I do for heatstroke in dogs?

It is essential to cool the dog down – but not too fast (see below). The basic first aid steps for heatstroke in a dog are MATCH:

M – Move them somewhere away from the heat. Carry them into the shade, or open the doors.

A – Airflow. Get some air moving over them – a breeze, or even fan them.

T – Telephone for advice – your vet will be able to advise you on the next steps.

C – Cool them with damp towels or tepid water.

H – Get Help – get them to your vet as soon as you can!


Should I break the window of a car that has a hot dog inside?

In the first instance, the advice of the police is to call them first on 101 or 999. If the dog’s life is in imminent danger you may have a defence in law against criminal damage… However, you might have to defend yourself in court.


Can heatstroke be treated?

In many cases, heatstroke is treatable, especially if the veterinary team can get to the dog before seizures start. Sadly, seizures in heatstroke often mean that severe brain damage has occurred. The vet’s focus will be on simultaneously treating the dehydration and, often, shock and cooling them down. Dogs with heatstroke always need to be seen by a vet, even if they seem fine. This is because problems like liver failure might not be immediately apparent.


If your dog is overheating, cool them and call your vet as soon as possible!