The day is hot and sultry, the kind of day when you work up a sweat by just breathing. A few minutes of vigorous activity, and you're swimming within your own shirt. But your dog only pants, with his tongue hanging out by at least a mile, to show he's hot also.
So whose body is better at keeping cool? The answer is, yours. It may be uncomfortable for you to sweat profusely, but it's an efficient method to regulate temperature. When it comes to keeping cool, we have it made in the shade compared to our dogs.
In people, sweat glands help regulate temperature by bringing warm moisture to the surface of the skin, which causes cooling as the water evaporates. Because sweat glands are located all over the human body, cooling takes place over a greater surface area of the skin than it does in dogs.
Dogs don't have the luxury of overall cooling because their bodies have very few sweat glands, and most of those are in the footpads. Dogs cool themselves primarily by the process of panting and breathing, with the moist lining of their lungs serving as the evaporative surface.
Most people believe that the dog's tongue contains sweat glands, but this is not true. The dog's tongue and mouth are associated with many salivary glands that produce different forms of saliva. Some cooling takes place as the panting dog moves air across saliva-moistened surfaces of the mouth cavity.
Dogs also dissipate heat by dilating (expanding) blood vessels in the face and ears. Dilating blood vessels helps cool the dogs blood by causing it to flow closer to the surface of the skin.
Excessive play on a hot day can lead to overheating (hyperthermia) and eventually to heat stroke. A dog's normal body temperature is within the range of 100.5 to 102.5 degrees Fahrenheit. If his temperature rises to 105 or 106 degrees, he may suffer heat exhaustion. At 107 degrees, heat stroke can occur, with potentially catastrophic consequences. Heat stroke can cause brain damage and even death.
A dog that is overheated will act sluggishly, or perhaps confused. His gums and tongue may appear bright red, and he will be panting hard. The dog may vomit, collapse, have a seizure, and may go into a coma.
An overheated dog is a real emergency situation. Get him to a veterinarian immediately. If possible pour water from the garden hose on him to begin the cooling process. On the way to the veterinary clinic, cover him with cool wet towels or spritz him with cool water. Don't use ice-cold water. For more information on what to do in case of overheating, see the article Be a Cool Owner: Don't Let Your Dog Overheat