5 months ago
Last edited at 8:23AM on 10/9/2013
Dogs don't have sweat glands like humans do. So in order to cool the body temperature they need to dispel warm air out of their mouth and pass cooler air across the tongue to help cool the blood thus creating a cooling effect of the entire body. It is not as efficient as having sweat glands like humans do ... that's why dogs are far more susceptible to heat than humans are.
That's yet again why it can be very harmful to a dog who is trying to pant but can't due to a muzzle. It can cause severe overheating.