Why don't dogs sweat?
Category: Biology Published: October 9, 2013
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Associate Professor of Physics at West Texas A&M University
Dogs do sweat. Sweating is a physiological response to heat where sweat glands secrete salty water. When the water evaporates, it takes energy with it, cooling down the organism in the process. Although dogs don't sweat profusely and visibly the way humans do, they definitely have sweat glands that secrete sweat in response to heat. The problem is that most dogs are covered with a thick coat of fur, so sweat secreted where there is fur would get trapped in the fur, fail to evaporate, and therefore fail to cool the dog down much. As a result, it is far more efficient for dogs to have sweat glands where there is little fur. For this reason, most of a dog's sweat glands are located on the pads of its feet and on its nose. On a hot day you may notice a dog leaving behind a trail of wet footprints as it walks across a smooth, dry surface. That's dog sweat.
With far fewer effective places for dogs to have body-cooling sweat glands as compared to humans, dogs must rely on another mechanism to keep cool. The primary cooling mechanism for dogs is panting. By breathing air quickly over the wet surfaces of the inner mouth and lungs, the dog's pants accelerate evaporative cooling in much the same way that a breeze across a sweaty person's skin speeds up cooling. Dogs also have a different kind of sweat gland all over their body. But the sweat emitted from these glands are used to counter rapid rises of temperature in localized skin patches that could lead to burns, and not to cool the body as a whole.
The Textbook of Small Animal Surgery edited by Douglas H. Slatter states, "Merocrine glands are coiled, simple, tubular glands found mainly in the footpads of dogs; they empty directly onto the epidermal surface. Sweat glands are better developed in the canine breeds that have long, fine hair. Sweat glands in the hairy skin of dogs and cats [apocrine glands] do not participate actively in the central thermoregulatory mechanism but protect the skin from excessive rise in temperature."