I have talked to some pet parents recently that wonder about a cough their dog gets when they get excited. It is a gag reflex known as reverse sneezing. She is forcefully inhaling to bring in air in through the nose and move mucus into the pharynx or throat. It can be caused by pulling on a leash, excitement, allergies, eating, or exercise intolerance. Some of the dogs do it when their parents' arrive. My Belle does it when I give her a bath. There is no reason to be concerned, unless or dog has a consistent cough.