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American Eskimo Dog standing in the grass in bright sunlight.
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Dogs are notoriously bad at dissipating body heat. Watch for early signs of heatstroke (also known as hyperthermia) in your dog to avoid serious outcomes.

What Is Heatstroke?

When a dog’s internal body temperature goes above a normal temperature of 101.5 degrees Fahrenheit (F), this is a fever and is called hyperthermia. When the body temperature is above 105 degrees F, the dog may be suffering from heatstroke.

Dogs have only a couple of ways to cool off—blood vessel expansion and panting. When dogs pant, they evaporate moisture from their tongues, nasal passages, and the lining of their lungs, and this cools them down as air passes over the moist tissue. They also cool off via vasodilation. Blood vessels, especially in the ears and face, expand,  bringing overheated blood closer to the surface to cool down.

The bottom surfaces of paws can sweat, but not enough to make a difference. “Heatstroke usually occurs when high ambient temperature overcomes the dog’s ability to dissipate heat. The degree of damage is determined by how high a body temperature is reached and how long the animal is exposed,” says Dr. Jerry Klein, Chief Veterinary Officer for the AKC.

Signs to Watch Out For

Heatstroke in dogs is life-threatening and can also result in very serious complications. Recognizing early signs of heatstroke may help you remedy the condition before things get too serious.

Early signs of heatstroke include heavy panting and rapid breathing, excessive drooling, dry mucous membranes, bright red gums and tongue, skin that’s hot to the touch, and a higher heart rate. Affected dogs become hyperactive and may have difficulty maintaining balance.

As exposure to excessive heat goes on, the dog’s condition worsens and includes signs of shock, pale mucous membranes with white or blue gums, a very rapid heart rate, and a drop in blood pressure. The dog hyperventilates, and dehydration becomes more severe. Pupils dilate, the pulse becomes more irregular, and the dog has muscle tremors. They may become lethargic and unwilling to move, urinate or defecate uncontrollably, collapse, and become comatose.

Golden Retriever laying down feeling lethargic.
stonena7 via Getty Images

Why Does Heatstroke Occur?

Heatstroke generally occurs during the hottest part of the year, especially when it’s humid. Contributing factors include:

  • Breed: Heatstroke can be seen in all breeds, but may be more likely in certain breeds, including longhaired and brachycephalic (short-nosed) dogs.
  • Age: Very young dogs, as well as older dogs, are more susceptible.
  • Physical fitness: Dogs that are out of shape are vulnerable when they exert a great deal of energy in excessively hot surroundings.
  • Weight: Overweight and obese dogs are more likely to suffer from heatstroke.
  • Medical disorders: Hypothyroidism, cardiac disease, and laryngeal paralysis also contribute to heatstroke.
  • Environment: The most common cause of heatstroke in dogs is confinement in a closed vehicle. The ambient temperature inside a closed car can become dangerously high in a matter of minutes, and the results can be fatal. Other causes of heatstroke can include being confined in an exercise pen or crate without fresh water in direct sunlight or for an extended period of time.
  • Water: Restricted access to water or not drinking enough water can cause overheating.
  • Acclimation: Sudden change to a warmer climate can cause heat stress.

How to Treat Heatstroke

Heatstroke therapy involves immediately trying to lower the dog’s body temperature. If you notice signs of heatstroke in your dog, it’s critical to stop any activity and help your dog cool down by:

  • Walking or carrying the dog to a well-ventilated, cool area.
  • Spraying or sponging the dog with cool (not cold) or tepid water, especially on the underside. Don’t immerse the animal in cold water.
  • Using a fan to blow cool air on them.

If you have a rectal thermometer, you should take your dog’s temperatureAccording to Dr. John Hamil, DVM, if the temperature is less than 105 degrees F, you should still consider this an emergency and immediately take your dog to your veterinarian.  If the temperature is higher than 105 degrees F, try to cool the dog down, and after a few minutes, retake the temperature. Don’t reduce the temperature below 103 degrees F, because the temperature may descend to critical levels.

Greyhound laying down on the rug.
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Bring your dog to your veterinarian as soon as the temperature reaches 103 degrees F or if you’re unable to reduce the temperature significantly. Severely affected dogs require fluids, medication, support, and oxygen. Complications may not occur immediately, so it’s important to let your veterinarian determine the type of follow-up treatment required.

Prevention Is the Best Medicine

Immediate action and correct treatment can mean the difference between a swift and complete recovery and long-term complications. Some veterinarians also advise that once a dog has experienced heatstroke, it’s more likely to reoccur.

Our dogs live to please us, and if we ask them to jog or hike or play catch, they’ll do it with enthusiasm, even on the hottest days. So it’s up to you to keep the weather in mind and limit the time your dog exercises in the heat. Choose cooler times of day for play or training sessions.

Always provide plenty of cool fresh water, shade, and frequent rest periods when it’s hot. And never leave your dog in the car. They may miss you, but they’ll be better off waiting for you at home.

This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.

Related article: How Long Can You Keep Your Dog Outside?
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