Why Does a Dog Pant? You have probably seen a dog panting on a hot day. When a dog becomes overheated, it sticks out its tongue and pants, or breathes heavily. Panting keeps a dog’s body from getting too hot.
A dog has very few sweat glands, so it cannot perspire to keep cool on a hot day, as we do. (You have many small sweat glands in your skin to help keep your body at the right temperature.)
A healthy dog rarely perspires at all. When a dog pants, its rapid breathing evaporates the moisture in its mouth. As the moisture evaporates, body heat is carried away, and the dog feels cooler.
But panting is also a warning sign. If your dog is taking a break from exercise and continues to pant heavily, this could be a sign of heatstroke. Another possible reason your dog suddenly starts to pant is as a symptom of illness.
While relaxing indoors, a dog may suddenly start panting if an electrical storm passes by. This is a normal fear response — dogs are easily startled by loud noises and bright flashes of light (such as with thunder and lightning).
Hot weather, getting spooked or not feeling well — dogs pant for all these reasons and more, including when they’re injured and in pain.