Written by Dr. Dennis Chew for Vetstreet

It always amazes me when, every year as the temperatures rise, there are still reports of animals being left alone inside hot vehicles, despite the fact that the dangers of doing so are well-known. Animals that exercise too vigorously in the heat or cannot seek relief from it are also at risk for illness and injury as well. Not too long ago, I had a concerning experience like this with my own dog when I took him out for a little fun in the dog park.That's why, as the dog days of summer arrive, I thought it might be helpful to review some simple facts about how the heat can affect our pets.

Balmy Weather? Still Deadly
It's important to realize that dogs and cats can develop heat-related injury quickly when they stay inside a parked car or other vehicle. This can happen even when the windows are partially lowered, the vehicle is in the shade, or the outside temperatures seem relatively moderate. Many people do not realize just how quickly the interior temperature of a car can increase to deadly levels, even with some airflow provided by cracked windows. For example, on a 90-degree day, the temperature inside a closed car can climb to 109 degrees within just 10 minutes. In less than 50 minutes, temperatures in that same car can rise to above 130 degrees. On even a comparatively balmy 70-degree day, temperatures inside a vehicle can reach triple digits within 30 minutes (see table).

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Heat toxicity can also occur in dogs that exercise too vigorously during periods of high heat, especially if the humidity is also elevated. Even dogs that are in good athletic shape and used to regular exercise can develop heat injury when out and about in extreme conditions. Heat toxicity, or heat injury, can run the gamut from heat exhaustion (which occurs in the early stages of a heat-related event) to heat stroke, which is a full-blown emergency that requires immediate veterinary intervention.

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What Happens To A Heat-Stressed Pet?
During heat stress, the animal's internal body temperature can increase rapidly, and fatal organ failure can follow. Since dogs and cats do not sweat (except on footpads and the nose) the way humans do, they cannot use this as a method to lower body temperature. Instead, dogs and cats try to regulate their body temperature by panting to help body heat dissipate. This response, however, is limited and easily overwhelmed under extreme conditions.

Signs Of Heat Stress
Initial signs of heat toxicity include:

  • Panting

  • Excessive salivation (which is often thick and ropey)

  • Weakness

  • Collapse

  • Bright red membranes of the mouth, tongue, eyes, and sometimes skin in light-pigmented dogs

  • Vomiting and diarrhea can also occur due to damage to the gastrointestinal tract

Multiple organs can fail if the excessive heat retention is not relieved soon enough. These organs include the gastrointestinal tract, kidneys, liver, heart, muscles, brain, and bone marrow. Heat retention causes the blood vessels to dilate, and a form of shock develops as the condition advances.

If the animal is in a state of collapse when found, it is imperative to get him to your local veterinarian or an emergency clinic immediately. Quickly cooling the animal for the trip with cool water from a garden hose may be helpful but do not immerse your dog in cold or ice water as this could lead to shock. If shock does develop, intravenous fluids and other medications may be needed for a few days upon arrival at the hospital.

Preventing Heat Stress
Never assume that it is OK to leave your dog or cat in a car unattended during warmer weather, and carefully monitor and limit strenuous exercise periods for your dog in high temperatures. Reduce the time you allow your dog to walk, run or jog with you, or to follow you during bike rides. If it's hot enough, you may need to postpone the activity altogether. Keep in mind that obese dogs or ones that only exercise occasionally are particularly vulnerable to overheating.

Even on a reduced exercise schedule, take frequent rest breaks in the shade. Remember to take water and even ice cubes along for your dog to drink when outdoor temperatures are above 80 degrees. Towels that can be wet with cool water and placed over your dog can help bring his body temperature down following exercise bouts — but be sure to remove the towels once they become warmed from body heat. Exercising in dog parks early in the morning or later at night when outside temperatures are lower will also reduce the risk for heat-related injury. Restrict exercise when outside temperatures are above 80 degrees, especially in locales with high humidity. Finally, dogs with long hair may benefit from being clipped or shaved for the summer months.

My Own Personal Experience
Recently, my own dog was vigorously exercising in the dog park -- running around with two other dogs and having a great time. The ambient temperature was about 92 degrees, and the humidity was quite high. He was fine for about five minutes, but then started to salivate a lot and was panting very rapidly. We removed him from the park and walked back to the car. He could not jump into the car on his own, and I had to lift him into the vehicle. He was extremely quiet and didn't move during the five-minute drive home. I kept the air-conditioning on high with the vents directed his way. Upon arrival at the house, I hosed him down for five minutes with cool water from the garden hose. He revived over the next 10 minutes. Had he not come around right away, we would have been on our way to the emergency clinic for IV fluids. This incident underscored for me just how easy it is for a dog to get into trouble in the heat -- even with a watchful veterinarian as an owner. If you see any potential signs of distress in your dog, be sure to take prompt steps to cool him. And if you have any doubt about how serious the situation may or may not be, call your veterinarian immediately.

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  • "I Hurt!"

    As you can imagine, this is a huge issue for veterinarians. Identifying pain can be hard to do when pets' pain-relieving adrenaline is pumping and they're obviously doing their very best to be sure that they don't show any weakness. Just so you know, dogs' and cats' wild ancestors imbued them with the ability to mask pain. This is an especially attractive quality when you live in mortal fear of predators who share your ecosystem. There's no time for visible suffering when a predator is looking for his next meal! <strong>More from Vetstreet:</strong> <a href="http://www.vetstreet.com/cats/meet-9-cat-breeds-who-crave-affection?WT.mc_id=cc_huffpo" target="_hplink">9 Cat Breeds That Crave Affection</a> <a href="http://www.vetstreet.com/our-pet-experts/my-top-three-most-reviled-seen-on-the-street-pet-owner-donts?WT.mc_id=cc_huffpo" target="_hplink">3 Bad Things Pet Owners Do That Drive Vet's Crazy</a> <a href="http://www.vetstreet.com/dr-marty-becker/dog-vs-cat-which-pet-is-better?WT.mc_id=cc_huffpo" target="_hplink">Are Dogs or Cats Better Pets?</a> <em>Flickr photo by <a href="http://www.flickr.com/photos/walkadog/3093763311/" target="_hplink">Beverly & Pack</a></em>

  • "I'm Itchy!"

    Although dogs will show you when their skin is irritated by chewing and scratching, cats are infinitely subtler. Most itchy kitties will display their discomfort by over-grooming. If the irritation is intense enough, hair loss can even result. It's only in the most extreme cases -- such as with ear mites and mange -- that cats will scratch to relieve itching, sometimes with claw marks to show for it. <em>Flickr photo by <a href="http://www.flickr.com/photos/rileyroxx/127381850/" target="_hplink">rileyroxx</a></em>

  • "That's More Food Than I Need."

    Can you imagine your food-obsessed dog ever confessing to this? The truth is that dogs, cats, goats and horses are the only species I know of that will eat themselves to death. It's kind of sad -- but true -- that most canines are capable of taking in as much food as we're willing to give them. And cats? That bottomless bowl of kibble that so many of their owners offer them means that they never have to ask for more. <em>Flickr photo by <a href="http://www.flickr.com/photos/australianshepherds/5768874645/" target="_hplink">carterse</a></em>

  • "I'm Tired."

    Lots of things can make a dog tired: hypothyroidism, Cushing's disease, diabetes, malnutrition, anemia, osteoarthritis, heart disease, cancer, fevers, etc. To you, it may seem like your pet is just getting old or settling into that couch potato middle age thing, but the truth of the matter may be more sinister. <em>Flickr photo by <a href="http://www.flickr.com/photos/trophygeek/7310041030/" target="_hplink">trophygeek</a></em>

  • "Why Do You Look So Fuzzy?"

    It's hard for pets to convey a loss of vision. While sudden blindness may lead to obvious signs of distress and confusion, a gradual loss of vision is hard to get a handle on if pets are good at adapting -- and they almost always are! <em>Flickr photo by <a href="http://www.flickr.com/photos/neekohfi/4483038146/" target="_hplink">neekoh.fi</a></em>

  • "I'm Nauseous."

    Here's a tough one. Unless pets are actively vomiting, most owners have a difficult time determining whether pets are nauseous. Guess what? So do veterinarians. If your pet is salivating, licking his lips constantly or swallowing frequently, nausea could be the culprit. <em>Flickr photo by <a href="http://www.flickr.com/photos/78428166@N00/3883142738/" target="_hplink">Tobyotter</a></em>

  • "I'm Too Hot!"

    When dogs pant hard and they lag behind on walks, it's time to stop. Many dogs will continue to walk, run or play until it's too late and heatstroke results. Cats are much smarter about this, but even they can hide overheating in confusing ways. Consider the feverish cat: Felines handle high fevers with sedated aplomb. They don't look like they're hot, and they appear as if they'd like nothing better than to sleep and hide. <em>Flickr photo by <a href="http://www.flickr.com/photos/mizzmurray/2628838578/" target="_hplink">lisamurray</a></em>

  • "My Paws Are Burning!"

    It happens when dogs are walked on hot pavement or sidewalks. It's amazing how they'll continue to walk when their feet are clearly on fire. Burnt pads are not only really painful, but they take weeks to heal. <em>Flickr photo by <a href="http://www.flickr.com/photos/allmightymo/78274346/" target="_hplink">Allmightymo</a></em>

  • "What Did You Say?"

    Hearing loss is not something that pets can communicate. We have to figure this one out on our own. <em>Flickr photo by <a href="http://www.flickr.com/photos/ddfic/5728328246/" target="_hplink">DDFic</a></em>

  • "Is It My Belly Or My Back?"

    Here's another tough one: Pets with back pain sometimes appear to have belly pain -- and vice versa. Part of the problem is that pets who have back or belly pain tend to show the same signs: They shiver, shake, fail to jump or run and generally don't act like themselves. Pets with either belly or back pain also react adversely when they're picked up from underneath, so it can be extra hard to figure out whether it's back or belly pain. <strong>More from Vetstreet:</strong> <a href="http://www.vetstreet.com/cats/meet-9-cat-breeds-who-crave-affection?WT.mc_id=cc_huffpo" target="_hplink">9 Cat Breeds That Crave Affection</a> <a href="http://www.vetstreet.com/our-pet-experts/my-top-three-most-reviled-seen-on-the-street-pet-owner-donts?WT.mc_id=cc_huffpo" target="_hplink">3 Bad Things Pet Owners Do That Drive Vet's Crazy</a> <a href="http://www.vetstreet.com/dr-marty-becker/dog-vs-cat-which-pet-is-better?WT.mc_id=cc_huffpo" target="_hplink">Are Dogs or Cats Better Pets?</a> <em>Flickr photo by <a href="http://www.flickr.com/photos/davemorris/6057980/" target="_hplink">Daveybot</a></em>

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  • "I Hurt!"

    As you can imagine, this is a huge issue for veterinarians. Identifying pain can be hard to do when pets' pain-relieving adrenaline is pumping and they're obviously doing their very best to be sure that they don't show any weakness. Just so you know, dogs' and cats' wild ancestors imbued them with the ability to mask pain. This is an especially attractive quality when you live in mortal fear of predators who share your ecosystem. There's no time for visible suffering when a predator is looking for his next meal! <strong>More from Vetstreet:</strong> <a href="http://www.vetstreet.com/cats/meet-9-cat-breeds-who-crave-affection?WT.mc_id=cc_huffpo" target="_hplink">9 Cat Breeds That Crave Affection</a> <a href="http://www.vetstreet.com/our-pet-experts/my-top-three-most-reviled-seen-on-the-street-pet-owner-donts?WT.mc_id=cc_huffpo" target="_hplink">3 Bad Things Pet Owners Do That Drive Vet's Crazy</a> <a href="http://www.vetstreet.com/dr-marty-becker/dog-vs-cat-which-pet-is-better?WT.mc_id=cc_huffpo" target="_hplink">Are Dogs or Cats Better Pets?</a> <em>Flickr photo by <a href="http://www.flickr.com/photos/walkadog/3093763311/" target="_hplink">Beverly & Pack</a></em>

  • "I'm Itchy!"

    Although dogs will show you when their skin is irritated by chewing and scratching, cats are infinitely subtler. Most itchy kitties will display their discomfort by over-grooming. If the irritation is intense enough, hair loss can even result. It's only in the most extreme cases -- such as with ear mites and mange -- that cats will scratch to relieve itching, sometimes with claw marks to show for it. <em>Flickr photo by <a href="http://www.flickr.com/photos/rileyroxx/127381850/" target="_hplink">rileyroxx</a></em>

  • "That's More Food Than I Need."

    Can you imagine your food-obsessed dog ever confessing to this? The truth is that dogs, cats, goats and horses are the only species I know of that will eat themselves to death. It's kind of sad -- but true -- that most canines are capable of taking in as much food as we're willing to give them. And cats? That bottomless bowl of kibble that so many of their owners offer them means that they never have to ask for more. <em>Flickr photo by <a href="http://www.flickr.com/photos/australianshepherds/5768874645/" target="_hplink">carterse</a></em>

  • "I'm Tired."

    Lots of things can make a dog tired: hypothyroidism, Cushing's disease, diabetes, malnutrition, anemia, osteoarthritis, heart disease, cancer, fevers, etc. To you, it may seem like your pet is just getting old or settling into that couch potato middle age thing, but the truth of the matter may be more sinister. <em>Flickr photo by <a href="http://www.flickr.com/photos/trophygeek/7310041030/" target="_hplink">trophygeek</a></em>

  • "Why Do You Look So Fuzzy?"

    It's hard for pets to convey a loss of vision. While sudden blindness may lead to obvious signs of distress and confusion, a gradual loss of vision is hard to get a handle on if pets are good at adapting -- and they almost always are! <em>Flickr photo by <a href="http://www.flickr.com/photos/neekohfi/4483038146/" target="_hplink">neekoh.fi</a></em>

  • "I'm Nauseous."

    Here's a tough one. Unless pets are actively vomiting, most owners have a difficult time determining whether pets are nauseous. Guess what? So do veterinarians. If your pet is salivating, licking his lips constantly or swallowing frequently, nausea could be the culprit. <em>Flickr photo by <a href="http://www.flickr.com/photos/78428166@N00/3883142738/" target="_hplink">Tobyotter</a></em>

  • "I'm Too Hot!"

    When dogs pant hard and they lag behind on walks, it's time to stop. Many dogs will continue to walk, run or play until it's too late and heatstroke results. Cats are much smarter about this, but even they can hide overheating in confusing ways. Consider the feverish cat: Felines handle high fevers with sedated aplomb. They don't look like they're hot, and they appear as if they'd like nothing better than to sleep and hide. <em>Flickr photo by <a href="http://www.flickr.com/photos/mizzmurray/2628838578/" target="_hplink">lisamurray</a></em>

  • "My Paws Are Burning!"

    It happens when dogs are walked on hot pavement or sidewalks. It's amazing how they'll continue to walk when their feet are clearly on fire. Burnt pads are not only really painful, but they take weeks to heal. <em>Flickr photo by <a href="http://www.flickr.com/photos/allmightymo/78274346/" target="_hplink">Allmightymo</a></em>

  • "What Did You Say?"

    Hearing loss is not something that pets can communicate. We have to figure this one out on our own. <em>Flickr photo by <a href="http://www.flickr.com/photos/ddfic/5728328246/" target="_hplink">DDFic</a></em>

  • "Is It My Belly Or My Back?"

    Here's another tough one: Pets with back pain sometimes appear to have belly pain -- and vice versa. Part of the problem is that pets who have back or belly pain tend to show the same signs: They shiver, shake, fail to jump or run and generally don't act like themselves. Pets with either belly or back pain also react adversely when they're picked up from underneath, so it can be extra hard to figure out whether it's back or belly pain. <strong>More from Vetstreet:</strong> <a href="http://www.vetstreet.com/cats/meet-9-cat-breeds-who-crave-affection?WT.mc_id=cc_huffpo" target="_hplink">9 Cat Breeds That Crave Affection</a> <a href="http://www.vetstreet.com/our-pet-experts/my-top-three-most-reviled-seen-on-the-street-pet-owner-donts?WT.mc_id=cc_huffpo" target="_hplink">3 Bad Things Pet Owners Do That Drive Vet's Crazy</a> <a href="http://www.vetstreet.com/dr-marty-becker/dog-vs-cat-which-pet-is-better?WT.mc_id=cc_huffpo" target="_hplink">Are Dogs or Cats Better Pets?</a> <em>Flickr photo by <a href="http://www.flickr.com/photos/davemorris/6057980/" target="_hplink">Daveybot</a></em>

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