Heatstroke in Dogs: Signs, First Aid, and Prevention

What causes it

In a large UK study of dogs seen by vets, exercise was the most common trigger by far. About three in four cases with a known cause started during a walk, a run, or play. Hot weather alone came next, followed by dogs shut in vehicles. A smaller number began in hot buildings, during vet or grooming visits, or when a dog was trapped under a blanket.

Exercise cases turned up in every month of the year, with a peak in July. A long game of fetch on a warm spring day can be enough. Parked cars are still a serious danger. In a US study, a dark car was left in the sun on days between 22 and 36 °C (72 and 96 °F). Within an hour, the inside grew on average about 22 °C (40 °F) hotter than the air outside. Most of that rise came in the first 30 minutes, and leaving the windows slightly open made almost no difference.

Dogs at higher risk

Any dog can get heatstroke, but some carry more risk. Flat-faced breeds such as Bulldogs, French Bulldogs, and Pugs have short, narrow airways, so panting cools them less well. In the UK data, Chow Chows, Greyhounds, English Springer Spaniels, Golden Retrievers, Cavalier King Charles Spaniels, and Dogues de Bordeaux were also at higher risk. Heavier dogs, dogs above the average weight for their breed, and dogs over 12 years old were more likely to be affected. Thick coats, breathing problems, and other health conditions add to the risk. Heatstroke during exercise mostly affects younger dogs, which tend to run and play harder and for longer.

Signs to watch for

Early signs are easy to mistake for a dog that is simply hot and tired. Watch for heavy panting that does not settle with rest, drooling, a bright red tongue and gums, and a dog that seems slow, stiff, or unsteady. A dog that lies down in the heat and does not want to get up needs your attention right away.

As heatstroke gets worse, you may see the following.

• Vomiting or diarrhea, sometimes with blood
• Weakness, stumbling, or collapse
• Gums that turn pale or bluish
• Trembling or seizures
• Confusion, not responding to you, or loss of consciousness
• Small red spots or bruises on the gums or skin, a sign of clotting problems

When it is an emergency

If you see any of these signs in hot weather or after exercise, start cooling and call the vet right away. Collapse, seizures, confusion, or blood in vomit or stool mean the dog is in serious danger. In UK research that graded cases by severity, nearly all dogs with mild signs survived. More than half of the dogs with severe signs, such as repeated seizures, unresponsiveness, or bleeding, died. Fast cooling and fast veterinary care give a dog the best chance.

First aid before the vet

UK veterinary researchers and animal welfare groups sum up the advice as "cool first, transport second." The longer a dog stays overheated, the more damage the heat can do. Start cooling where you are, and call your vet or the nearest emergency clinic as soon as you can.

Move the dog out of the sun into shade or a cooler room. Pour cool or cold water over the whole body, keeping it away from the head. Water straight from the cold tap is fine, and there is no need to wait for lukewarm water. Moving air from a fan, an open window, or a breeze helps the water carry heat away. A young, healthy dog that is conscious can also be placed in a bath or paddling pool, with the head held well above the water. For older dogs and dogs with health problems, UK guidance favors pouring water and moving air instead.

Do not drape wet towels over the dog. They can trap heat against the body, and they cool much more slowly than pouring water. A wet towel underneath the dog is fine. Keep water out of the nose and mouth. If the dog is alert, offer cool water to drink, but do not force it. Never leave a confused or unconscious dog alone in water.

Keep cooling until the heavy breathing starts to settle, and ask your vet on the phone how long to go on. Then travel to the clinic in a cool car with the air conditioning on or the windows open, so the dog keeps cooling on the way. Make sure the dog cannot jump out. A vet check is recommended even if your dog seems to recover fully, because damage to the kidneys, liver, gut, or blood clotting may not show from the outside. For other emergencies, such as bleeding, choking, or burns, see first aid for dogs and cats.

How vets diagnose and treat it

Vets usually diagnose heatstroke from the story of what happened, the dog's temperature, and a physical exam. The temperature may already be lower by the time you arrive, so tell the vet how long the dog was in the heat and what cooling you did. Blood and urine tests, including tests of blood clotting, help show whether organs have been affected.

Treatment depends on how sick the dog is. It often includes more cooling with water and fans, intravenous (IV) fluids, and oxygen. Some dogs need medicines to control seizures or protect the gut, and some need sedation or anesthesia to support their breathing. Dogs with severe heatstroke may need to stay in the hospital so the team can watch the kidneys, liver, and clotting. After going home, a dog usually needs close watching for a day or two and a follow-up check. Many dogs recover with prompt care. Some are left with lasting organ damage that needs long-term care.

How to prevent it

Heatstroke is much easier to prevent than to treat. These habits help on warm days.

• Walk early in the morning or late in the evening, and shorten or skip walks on the hottest days.
• Keep fetch and running games short, with rest breaks in the shade. Some dogs keep playing long after they should stop.
• Stop exercise if your dog pants very hard, struggles to breathe, or slows down and does not want to go on.
• Make sure your dog always has shade and fresh water, indoors and out.
• Never leave a dog in a parked car, even for a few minutes or with the windows open.
• Keep your dog at a healthy weight.
• Avoid hot pavement and sand, which can also burn paws.
• Use fans, cooling mats, and good airflow at home.
• For flat-faced dogs, use a harness instead of a collar and take extra care in any warm weather.
• Ask your vet or groomer whether a trim suits your dog's coat.

Heatstroke is not an infection, so it cannot pass from one animal to another or to people. The same heat can harm everyone exposed to it, though. If one dog overheats in a car, yard, or room, check the other pets there too, and look after yourself as well.

Rescued and newly adopted dogs

The first stops after every Paw Squadron rescue are the vet and a bath, and every animal gets a checkup, treatment, vaccinations, and a microchip before adoption. A new family still needs time to learn how their dog copes with heat. You may not yet know how far your dog can walk on a warm day, how quickly it tires during play, or whether its weight, shape, or breathing puts it at higher risk.

During the first summer, keep walks short and in the cooler hours, and watch your dog closely. If your new dog is traveling to you in hot weather, plan for shade, water, and breaks, and never leave the dog alone in a parked vehicle during stops. At the first visit, ask your vet whether your dog's breed, build, or health calls for extra care in the heat. You can find more care guides in PawPedia, and dogs looking for homes on our Adoptions page.