It is a common sight to see a dog panting. Dogs pant in health and in sickness. In health, a dog pants because of a dog's cooling system. When humans sweat, the moisture released on the skin's surface cools as it evaporates and in this way, humans can lose excess heat from their body. Unlike a human sweat system, a dog's body can only cool itself mainly through an evaporation system that involves the dog's tongue. Although a dog's body does have sweat glands located on the pads on a dog's feet and ears, the dog's body is cooled off mainly through its tongue. As a part of its cooling system, the dog cools its body by cooling the fluids in its mouth by providing a steady stream of air against the tongue. This cools the blood vessels in the dog's head area. Although a dog's cooling system is adequate for its needs, a dog may suffer from heatstroke or too much heat. A dog that needs to be cooled will start to pant more than usual. A dog's body needs lots of water so that its cooling system will run efficiently. A dog that does not receive enough water is prone to illness caused by the heat. The more water that a dog has available to cool, the better the dog can cool its body. Other reasons that can cause a dog to pant are excitement, stress and exercise. Some dog breeds with a shortened face will tend to pant more than other breeds of dogs. Seizures, lung and heart disease may also cause a dog to pant. By giving your dog enough water and doing what you can to prevent overheating in the hot weather, you can help a dog's cooling system to keep the dog cool. Panting cools your dog's body off and a dog's cooling system will run well with enough water in a dog's diet.