Causes of excess panting in dogs include heatstroke, poisoning, chronic illness and injury or pain, according to WebMD. Some canine medications can also lead to excessive panting.
Heavy panting can be an ominous sign that something is wrong with a dog, notes WebMD. While a dog may pant or breathe heavily after exercise, heatstroke can also cause panting. Other signs of heatstroke in dogs include weakness, glassy eyes, fast heart rate, seizures and vomiting. Heatstroke in dogs requires immediate evaluation by a veterinarian and steps to cool the dog down.
Chronic illness in dogs can cause heavy panting, according to WebMD. Illnesses such as heart failure, Cushing’s syndrome, pneumonia and laryngeal paralysis can cause panting and heavy breathing. Low levels of blood calcium, eclampsia and allergies are other causes of heavy breathing.
Some panting in dogs is completely normal, advises WebMD. Dogs use panting to cool off, and they tend to pant when they are hot, energetic or excited. Some dogs, including pugs, Boston terriers and bulldogs, are naturally prone to heavier breathing due to the size of their snouts. However, panting is cause for alarm it begins suddenly, is intense and constant, or if the dog is in pain.