Dogs have no sweat glands. They don't release excess water and salts from circulation in the body through them as many mammals are won't to do with the exception of hogs and hippos. They sweat through their mouths and thats why they can be seen panting in hot weather. They open their mouth in an effort to cool themselves since this is one of the primary functions of sweat. Thats why in hot weather, I take my dogs out for a swim and I can see the excitement on their faces. They really relish the activity. Lack of sweat glands should be one of the reasons we should groom dogs to remove grime from their coats and afford them a chance to relax.
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