My dog's cough improved, but still congested after sniffing. Why?

Hello and thank you for reaching out to Petco Pet Education Center, formerly Petcoach. Coughing can be caused by primary lung disease, such as pneumonia, asthma, or cancer; problems with the heart; and diseases of the trachea or windpipe itself. If Nacho is improving at home, you can likely continue to monitor him for any progression or worsening of his clinical signs. If he is eating and drinking normally at home, and acting normally, it is less likely that he is sick with something like pneumonia. If he continues to cough, however, I recommend having him seen by your veterinarian, to evaluate for any evidence of underlying heart disease or potential asthma. I hope this is helpful - best of luck with Nacho!