Dogs pant for a few reasons, but besides being hot, usually due to exertion, excitement or stress.
Of course dogs will pant when they get hot or exert themselves because this is the main way they get rid of body heat. Although they can eliminate a small amount through their paws too, dogs can't sweat like people. Panting helps them circulate fresh, cool air within their bodies to help them cool down.
Many times a dog will pant when the temperature is not a factor, rather it's a matter of stress. Any excitement is a level of stress to a dog, so even if you think the situation isn't "bad"- like riding in the car to go to the park- it can still be stressful to your dog. If your dog is put in a new situation or somewhere they may be uncertain or uncomfortable, they may begin panting as a displacement behavior and or because they are getting worked up/ hot because of the stress.
Other stress signals/ displacement behaviors that may happen in those instances too are lip licking, yawning and scratching- which are all ways the dogs are trying to cope with the situation they are in and relieve their anxiety. Looking for these other cues is one of the ways you can assess the situation to determine if the panting may be about stress or not.
Most panting is relatively innocent however, a dog that pants excessively in certain situations- ie when you take them places, ride in the car or when you leave them- are definitely experiencing some levels of anxiety that may benefit from management support.
In my humble opinion, if your dog is stressed enough to pant often, then they probably need you to help them find a way to feel more comfortable in their own skin.
They deserve to enjoy life and not feel on edge all the time, so looking at it from that perspective can help- since many people understandably, don't want to "drug" their dogs. However, if your dog can't "relax" even when there's nothing wrong, you owe it to them to think bigger than your ideals and think more along the lines of what your dog might NEED.
Giving your dog their best life may indeed involve some kind of support for their anxiety- but this is also nothing to feel bad about either!
Support could be something used acutely, before a stressful event, like an herbal supplement, or perhaps CBD- which we have found in our many rescue animals, can be very beneficial for generalized animal anxiety. Some dogs may require a more long-term, continuous strategy however too- even pharmaceuticals- if they are panting a lot during their average day and it cannot be attributed to a medical condition.
Panting can be serious if it is related to a medical issue. This would be if panting happens in normal situations where the dog used to be comfortable- for example, at home. Dogs that seem to have "no reason" to be uncomfortable or hot in a situation they never were before, may indeed be having some kind of change in their health that needs to be addressed by a vet visit.
In all, dogs should not pant excessively. If your dog is, you need to start to take notes on when this is occurring and get to the vet, first and foremost. By ruling out a health condition first as well as documenting the situation otherwise, you can out together a bigger picture of all the factors involved and get to the bottom of your dog's panting!
-jme, Executive Director, Motley Zoo Animal Rescue