There are many reasons why a dog might breathe heavily. While it can be a common occurrence in warm weather, there are other more serious conditions that could be indicated by increased breathing rates. Before you take your dog to the vet, evaluate his symptoms to try and decipher what his heavy breathing may mean.
Overheating and Exertion
The most common reason for a dog's heavy breathing is from overheating or exertion. Since dogs don't sweat, they cool themselves by panting and will breathe harder in hot weather or after a lot of exercise. Heavy breathing in these situations is easily remedied by having plenty of cold, fresh water available for your dog to drink. However, if your dog has been out in the sun for a long time on a hot summer day, there is a possibility that your dog has developed heat stroke. Signs of heat stroke are vomiting, staggering, bright red tongue and diarrhea coupled with heavy breathing. If your dog seems to be suffering from heat stroke, cool him down by spraying or immersing him in cool water and placing him in front of indoor fans.
Anxiety & Stress
Just like humans, animals are susceptible to the effects of stress and anxiety. If a dog is in a new home or environment or is surrounded by strangers, he may feel anxious and breathe more heavily than normal for the first couple weeks in the new place. He can be calmed by giving him more than average love and affection.
Pain & Infection
If your dog has suffered an injury, the pain may be causing heavy breathing. Perform a body check of your dog to see if there are any cuts, wounds or sensitive areas that cause him pain. You may also want to have your vet perform a heartworm check, since advanced heartworm infections can cause coughing and heavy, labored breathing.
Congestive Heart Failure & Fevers
More serious ailments like fevers and congestive heart failure can also cause heavy breathing. If your dog is panting heavily while he is still, it's possible that he has a fever from a viral infection. You should take him to the vet if his body temperature is over 102 degrees. Congestive heart failure occurs when there is not enough oxygen reaching the blood cells in your dog's body and fluid begins to build up in the lungs. The ailment can worsen over time and if you suspect your dog's heavy breathing is due to heart failure, take him to your vet for diagnosis and treatment.