“Dogs sweat by salivating.”

It's a common sight on a warm day: a dog panting heavily, tongue lolling, perhaps with a bit of drool. This visual often leads people to believe that dogs "sweat" by salivating, much like humans sweat through their skin. While the wetness around a dog's mouth is indeed part of their cooling process, the idea that salivating is their equivalent to human sweating is a widespread misconception. The truth is more nuanced, and dogs have multiple ways of regulating their body temperature.

Scientifically, dogs do possess sweat glands, but they are not distributed across the body in the same way or for the same primary purpose as human sweat glands. Dogs have merocrine sweat glands located predominantly in their paw pads. These glands release a watery sweat that, upon evaporation from the hairless pads, helps in a minor way to cool them down. You might even notice damp paw prints on a hot day, which is evidence of this process. Additionally, dogs have apocrine glands spread over their entire body, but these are mainly responsible for producing pheromones for communication with other dogs, not for significant body cooling.

The mistaken belief that dogs sweat through their mouths likely stems from observing their most prominent cooling behavior: panting. When a dog pants, they rapidly inhale and exhale, which causes moisture from their tongue, nasal passages, and the lining of their lungs to evaporate. This evaporation carries heat away from their body, effectively cooling them down. Another crucial method dogs use to beat the heat is vasodilation, where blood vessels, especially in areas like the face and ears, widen to bring warm blood closer to the surface of the skin, allowing heat to dissipate into the environment. Therefore, while a wet tongue is involved in cooling, it's the act of panting and the evaporation of saliva, rather than "sweating" from the mouth, that truly makes a difference.