Heat-related illness  is a spectrum of injury caused when the dog's body is unable to cope with elevated body temperatures (hyperthermia) which can result in internal damage to multiple organ systems. The most severe degree of heat-related illness is heatstroke-which is generally considered to be a body temperature greater than 106°F with central nervous system dysfunction. However, a body temperature of 106°F, it is Not always the best indicator of heat related-illness. Acclimated and athletic dogs may have body temperatures at or near that value but still be okay for a time, while other dogs may actually start suffering from heat-related illness, even heatstroke, at body temperatures lower  than the defined 106°F.  Therefore it is very important to monitor your dog's behavior and appearance for early signs of heat-related illness so you can take steps to reduce their body temperature and prevent worsening of the condition.
Many dogs will overexert themselves in order to please you or for the love of play- Do not expect your dog to self-regulate and stop when they need to.

 There are four methods a body can use to cool itself.

1. Convection occurs with air flow over the body. This is why you feel hotter running on a treadmill, running in place doesn't create any air flow.
2. Conduction occurs when heat is transferred from one object to a cooler object. Think lying on a cool tile floor.
3. Radiation is the loss of heat to the surrounding environment/air. This is most effective when the environmental temperature is lower than the body temperature.
4. Evaporation "carries" heat away as water evaporates. This works better in lower humidity environments.

In people (and some animals like horses) sweating is a significant source of evaporative cooling. The density of capillaries (small blood vessels) near our skin surface is high compared to dogs because we use sweating over our entire bodies for cooling. Dogs do lose a significant amount of heat across their skin but they have a lower density of capillaries near their skin surface (paw pads excepted) and because dogs don't sweat like people and horses do, their skin surface heat loss is relatively static (they can't really increase how much heat they lose through this method). In dogs, evaporative cooling is achieved  almost entirely through panting as the saliva and moisture of the mucous membranes of the respiratory tract allow for evaporation. And panting is something a dog has some control over. This is why panting becomes an important indicator for how hot a dog has become.

Hyperthermia is an abnormally high body temperature that occurs when a dog's body generates or absorbs more heat than it can release and can result in heat-related illness. Heat stress and heat exhaustion are early forms of heat-related illness (but they may still have internal damage) while heatstroke is the most severe and immediately life threatening condition.
Exertional heat-related illness occurs when a dog performs intense or prolonged activity in a hot environment. Here in Arizona, hyperthermia is a very real risk even for dogs that aren't significantly exerting themselves because the environment is so hot or the dog is in the heat for a prolonged period (this is called environmental heat related illness--this is why dogs die in hot cars). These are not mutually exclusive, you can have exertional and environmental conditions that both contribute to the development of heat-related illness.
No matter how the dog becomes overheated, the risks of severe heat-related illness remain the same. It triggers a sequence of biological processes that result in harm to various organs, internal bleeding, breathing difficulties, neurological issues, and ultimately, death. These injuries may not be immediately apparent during the heatstroke incident, but their effects can still manifest even after the dog has been cooled down. Treating heatstroke goes beyond just cooling them down and veterinary care is critical in these cases. In addition to cooling your dog down, the veterinary team will need to address fluid imbalances, provide oxygen, and may need to hospitalize your dog in order to manage the bleeding disorders and organ damage that have occurred.  This is why it is very important that you seek veterinary attention ASAP if you suspect your dog has suffered from heat stroke.

Signs of heat stress or  heat exhaustion:
You can consider the following as early signs that your dog is getting overheated and may be in the early stages of heat-related illness (heat stress and heat exhaustion) and you need to let them rest, get them to a cooler environment and cool them down to prevent progression to heatstroke.  While some dogs in these early stages may recover if cooled and provided access to drinking water (but don't force them), a veterinary evaluation may still be warranted as these are still signs that some degree of  heat-related illness could have occurred.

• Seeking shade/cooler location
  
• Trying to rest, seeming tired, slowing gait- instead of sprinting after a ball, you may notice your dog has started trotting or even walking. They may try to lay down between throws or not immediately return the ball. If you are walking together they may slow down or try to rest. Notice- were they walking beside you but now they are starting to fall slightly behind--or are they trying to walk in the shade of your shadow even?
• Subtle changes in behavior like failed or delayed responses to known ques or commands
• Heavy Panting- As panting is a significant cooling method for dogs you can get a good idea of how hot they are getting by how their panting changes. Overheating dogs will pant heavily and  near constantly (See "uncontrolled panting" for heatstroke below)
  •  Panting "grin"- They may look like they are grinning as they pull their lips as far back as they can to expose as much evaporative surface area as they can. They may even be holding the "grin" so tight it looks like they are squinting their eyes.
• Tongue changes- As a dog gets hotter, their tongue may elongate, get wider and flatter or curl upward- all efforts to increase surface area to increase cooling.

While these are "early" signs they are not all or none. Don't wait until their heavy pant becomes a full "grin" before you determine they are too hot. If you start to see any of these signs it is a good indication to let them rest  (or make them, as we know some dogs won't stop on their own). Move them to shade or indoors and provide drinking water (but do not force them to drink).  If you can, use a hose or tub to soak them and fan them to provide air movement to  maximize evaporative cooling.
Signs of heat stroke:
Signs of early heat-related illness can still be seen once it progresses to heatstroke, but the neurologic and bleeding signs listed below are more specific indicators of heat stroke and an outright emergency. If you see any of these signs in your dog-- stop what you/they are doing, start cooling them down and take them to the nearest available emergency clinic ASAP.

• Uncontrolled panting- You might notice how normally your dog stops panting so they can sniff something interesting. If you offer your dog something to sniff or a treat and they can take a break from the panting to sniff or take a treat they still have control of their panting. If they do not stop this means they can no longer control their panting. Their body is trying to maximize heat loss and panting has become too vital to interrupt--at this point that earlier sign "heavy panting" has progressed to a sign that they have reached heatstroke.  This is a good example of the progressive nature of these signs and why it is important to catch the signs and take action early.
• Gum and tongue color change- red, pale, or blue
• Altered mentation- acting confused, dizzy or lethargic
• Stumbling or collapse
• Seizures
• Vomiting and/or diarrhea which may or may not be bloody
• Hypersalivation (excessive drooling or thick saliva)
• Patchy discoloration of the skin (see image)

 

 Cool first, then transport
** If you even suspect your dog may be suffering from heat stroke--  start cooling and get them to an emergency visit with your vet or an emergency clinic ASAP. ** Let them rest if they are suffering from exertional heat stroke. Move them to a shaded area or indoors. In an otherwise healthy, conscious dog use water immersion (don't submerge their head). If your dog is unconscious, seizing or has significant health conditions (other than the current heat illness) a hose and fan may be a better option. If you can't monitor your dogs temperature aim for ~ 5 minutes of cooling before transporting. The longer a dog's temperature remains elevated the more damage is done so if you are transporting a hot dog it is still incurring damage on the way to the vet. On your way to the vet either have the a/c on full blast or have the windows down. 
If transport is going to be delayed- which is not recommended if avoidable- for any reason and you have a thermometer you can cool them until the their temperature reaches 104°F.

Water for cooling
Partial water immersion (do not submerge the head) is the fastest way to cool a dog. Make sure you feel the water first -remember water in hoses can get very hot here in Arizona. Make sure that a dog being cooled is under constant supervision as their condition can deteriorate if their high body temperature has caused significant enough damage.
Any water that is cooler than the dog will help them cool. Studies have shown that immersion in water even as warm as ambient conditions provided faster cooling than other methods such as fans alone or isopropyl alcohol on the paws. But do not be afraid of using cold water, it will not push your dog into a worse crisis- It is the heat that is injuring them. Cold water will cool them fastest and get them out of the dangerously high temperature which is critical. Since you are starting the cooling process and transporting them asap, the faster you can reduce their body temperature the better. Again, the longer their temperature remains elevated the longer they are incurring heat related damage. Cool them for ~ 5 minutes then transport to a veterinarian immediately.

If your dog is otherwise healthy and conscious, go for water immersion. If your dog is very young or old, has other health conditions, or is unconscious or seizing- use a combination of hosing and air movement for evaporative cooling since drowning or water inhalation is a higher risk in these cases.

While any  dog can suffer from heat-related illness there are some factors that can make some dogs more at risk than others

• Breed- brachycephalic (flat nosed) dogs are at increased risk of heat illness as they have less surface area for heat loss through panting and generally have other factors that compromise their cardiorespiratory function which is essential in heat regulation. Golden and Labrador retrievers are also commonly seen in large scale studies of dogs with heatstroke as well as working breeds like belgian malinois and german shepherds. This is likely due to their playful natures, high drive and/or work conditions.
  
• Age- very young or old dogs are at higher risk as their ability to thermoregulate can be reduced
  
• Bodyweight >15 kg (33 pounds)
  
• Cardiac disease
• Obesity
• Tracheal collapse or laryngeal paralysis
  
• Lack of physical fitness and/or heat acclimation
  

Preventing heat-related illness is much better than trying to treat it. Here are some tips to help avoid this life threatening condition
1. DO NOT leave dogs in cars.  According to the national weather service, even on a pleasant day with outdoor temperatures in the 70s (°F), the interior of a car can reach 100°F in minutes.
2. Exercise dogs only in the coolest part of the day and for short periods. Here in Arizona that's the early morning before or right around sunrise.
3. Ensure adequate access to water, shade or cooler environments

Veterinary Tactical Group
Canine Heat Injury Prevention & Field Treatment 

Hanel RM, Palmer L, Baker J, et al. Best practice recommendations for prehospital veterinary care of dogs and cats. Journal of Veterinary Emergency and Critical Care. 2016;26(2):166-233. doi:https://doi.org/10.1111/vec.12455

Bruchim Y, Horowitz M, Aroch I. Pathophysiology of heatstroke in dogs – revisited. Temperature. 2017;4(4):356-370. doi:https://doi.org/10.1080/23328940.2017.1367457

Parnes SC, Amritha Mallikarjun, Ramos MT, Stone TA, Otto CM. A Randomized Cross-Over Study Comparing Cooling Methods for Exercise-Induced Hyperthermia in Working Dogs in Training. Animals. 2023;13(23):3673-3673. doi:https://doi.org/10.3390/ani13233673

Hall EJ, Carter AJ, Bradbury J, et al. Cooling Methods Used to Manage Heat-Related Illness in Dogs Presented to Primary Care Veterinary Practices during 2016–2018 in the UK. Veterinary Sciences. 2023;10(7):465. doi:https://doi.org/10.3390/vetsci10070465

Casa, Douglas J.; McDermott, Brendon P.; Lee, Elaine C.; Yeargin, Susan W.; Armstrong, Lawrence E.; Maresh, Carl M.. Cold Water Immersion: The Gold Standard for Exertional Heatstroke Treatment. Exercise and Sport Sciences Reviews 35(3):p 141-149, July 2007. | DOI: 10.1097/jes.0b013e3180a02bec

US Department of Commerce N. Heat, Autos, and Safety. www.weather.gov. https://www.weather.gov/lsx/excessiveheat-automobiles

Tis the season for holiday gatherings and all the excitement, adventure, noises and smells that often accompany our visiting family and friends. It’s important to remember, while some pets may be overjoyed with everything, for many it can be overwhelming and stressful.

If your pet is one that doesn't delight in the bustle of holiday get-togethers, one way you can help is by ensuring they have a safe space where they can relax and get away when they need to. Even those who seem completely comfortable may appreciate a retreat on occasion.