When people get hot, they sweat. The sweat evaporates, cooling our bodies. Dogs have sweat glands too, but most of them are on the pads of their feet, and they only play a small role in cooling. Panting is their main way of getting rid of excess heat. Instead of evaporating sweat, they use evaporation from their tongue, mouth, and lungs to cool down. They can increase blood flow to their mouths to cool the blood faster, which often causes the mouth of an overheated dog to appear bright red.