Why do dogs pant?
Panting as a cooling mechanism is necessary because dogs do not have an effective system of sweat glands like people do. Instead, dogs cool their bodies using the evaporation of moisture from the mouth and tongue and exchange the hot air of their lungs with cooler external air.
Panting should not be confused with labored breathing. Labored breathing is characterized by strained respiration and may be accompanied by sounds of distress like crying or whining, or whistles from the nostrils or windpipe due to blockage.