Dogs produce saliva and foam at the thought of food, sight of food and while playing, running and walking. Dogs will also produce saliva and foam when in the presence of other dogs, company, or situations that make the dog feel fearful or stressed.
Covered in hair and with a cooling system involving the feet and the saliva, the dog can overheat easily. The dog has an evaporation cooling system that involves cooling off the saliva on the tongue. The other ways that the dog releases heat is through its breath and the sweat from the pads of the dogs feet.
Dogs sweat glands, unlike a humans sweat gland system, which involves most of the skins surface, release sweat for cooling purposes only from the pads of the feet. The dog will sweat when it is hot or excited. A dog pants to draw air over and cool the surface of its tongue.
A dog can be overheated while running, particularly in hot and humid weather. While running, a dog will pant, salivate and even foam, as the body works to cool. If a dog is running on hot pavement or road, the dogs foot defense against overheating will have difficult cooling the dog.
When you see a dog salivating in the heat, its body is trying to cool itself down. You can help keep your pets body temperature down by providing extra water on hot days. Your dog should not take long runs in the summer as it could cause overheating, which can be a life threatening condition for your dog. In hot weather, you can take your dog for exercise in during the cool morning or evening hours.
Foaming at the mouth can be caused by medical conditions such as poisoning, irritated mouth, obstructed throat, lesions, local ulcers and paralysis in the voice box or mouth. Rabies also causes foaming at the mouth. If foaming at the mouth occurs in a dog that does not normally produce much saliva, seek the attention of your veterinarian.
Your dog needs enough water regularly to keep its cooling system in good order. When your dog is running, you will have to provide it with extra water to make up for the water that is lost through the cooling action of the extra saliva and foaming that occurs. You may also want to leave your dog at home when you run in the summer so that you can avoid overheating your dog. A safer alternative for exercise sessions can be a grassy, shaded area during cooler hours or in your yard with a small pool filled with water.