A cough that lasts for 8 weeks or longer. It may occur with other symptoms, including a runny or stuffy nose, extra mucus in the back of the throat, wheezing, shortness of breath, or heartburn. A chronic cough may be caused by allergies, sinus infections, asthma, gastroesophageal reflux disease (GERD), or other conditions. It may also be caused by smoking tobacco or by breathing in secondhand tobacco smoke over a long period of time. It usually improves when the problem that caused the cough is treated. For example, a chronic cough may get better when a person quits smoking.