Thank you for your question regarding your 5 year old male American Eskimo who seems to be excessively panting. As you can probably well imagine, there are many different things can cause constant panting. Heavy panting can be caused by heart problems, lung problems, fever, or bronchitis. You can read about this here: http://www.petplace.com/dogs/panting-in-dogs/page1.aspx
Dogs pant for various reasons. They pant to cool down (which you have tried to rectify but with no change in the symptom), but they also pant when they are under stress, in pain, or afraid. There can also be medical causes such as neurological problems, respiratory disorders, and heart problems such as heartworm, anemia, and fever, and even sometimes a toxicity! Sometimes in older dogs, there can even be a tumor to blame - although do not panic as this is a lot rarer than the other problems I have mentioned and your boy is only 5!If your dog is panting but has no other symptoms, keep a watch on him. If it still seems excessive after a day or so, has been ongoing over a period of months, or if he develops more symptoms, then please schedule an appointment with your Vet to get him fully checked over. It could well be that your boy's panting is indeed NOT excessive and that he is clinically normal for a large breed dog. Be sure to have plenty of water bowls available for him also. I definitely would encourage a Veterinary visit just to ensure there is not something else going on here.
I hope this has been of help and please reply if you need more info.
Dr M D Edwards