Dogs do not sweat in the same way as humans.This is why so many muzzled dogs die in the heat……………………
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A dog's body temperature is controlled by her brain. When there are increases in outside temperatures or a dog is excited, stressed, or has been exercising, her body gets a signal from her brain to lose the extra body heat. In humans, this usually results in sweating.
Dogs do have some sweat glands, but they are much fewer than in humans and their skin is covered in fur, so this minimizes the amount of cooling the sweat can provide.
The most sweat glands in a dog are around her paw pads. You may see damp footprints from your dog walking on a hard surface in the summertime.
Panting is the most efficient way dogs have to cool themselves. It works by allowing heat from the hottest part of the body, the inner thorax, to escape through moisture produced by the mucous membranes of the tongue, mouth, and throat. The dog exhales the moist air, and the process of evaporation cools the dog.
If these processes cannot be performed or the body is overwhelmed and cannot cool itself enough, heat stroke and death may occur.
http://www.doghealth.com/how-and-why/how-dogs-sweat