Heatstroke in dogs is not mostly about hot cars

Every summer brings the same campaign: do not leave your dog in a car. It is good advice. It is also aimed at a small minority of the cases that actually put dogs in a veterinary clinic.

What the data says

Hall, Carter and O’Neill examined records for 905,543 dogs under primary veterinary care across 886 UK practices. Of 879 heat-related illness events where a trigger was identified, 652 — 74.2% — were exertional, caused by exercise. Environmental heat accounted for 113 events (12.9%). Vehicular confinement accounted for 46 (5.2%). The paper is titled, bluntly, "Dogs Don’t Die Just in Hot Cars".

The vehicle cases are deadlier, but far rarer

Judged by case fatality the ranking inverts: 10.8% for vehicular confinement, 9.5% for environmental, 7.6% for exertional. A dog shut in a car is in more danger per incident. But because exertional cases are so much more common, exercise affected and killed almost ten times as many dogs. Both facts are true, and only one of them is on the posters.

Who is most at risk

In the companion incidence study, brachycephalic — flat-faced — dogs had 2.10 times the odds of heat-related illness compared with mesocephalic dogs. By breed against Labrador Retrievers, Chow Chows carried 16.61 times the odds, Bulldogs 13.95, and French Bulldogs 6.49. Overall incidence was 0.04% of dogs in a year, with a 14.18% case fatality rate.

What actually reduces the risk

• Move walks to early morning or late evening in hot weather, and shorten them rather than slowing them.
• Let the dog set the pace. Exertional heatstroke happens when a dog keeps going past the point it should have stopped — usually because a person is still throwing the ball.
• Carry water and offer it before the dog looks like it needs it. A bottle that pours into its own bowl gets used; one that requires a separate bowl often stays in the bag.
• Give a cool surface to lie on afterwards. Dogs shed heat by panting and through contact, and a floor that is cooler than they are does real work.
• Learn the early signs — heavy panting that does not settle, thick drooling, unsteadiness. Core temperature at or above 41.0 °C is where cellular damage begins.

Why this matters more than the car warning

Almost everyone already knows not to leave a dog in a parked car. Far fewer people know that a normal walk on a warm day, with an enthusiastic dog that will not stop on its own, is statistically the more common route to the same emergency. That is the gap worth closing.