Chronic cough is the scourge both of the coughers themselves, and the doctors who treat them. Although rarely medically serious, chronic cough can be surprisingly debilitating by disrupting sufferers' social and professional lives. Doctors, for their part, often feel frustrated and powerless in treating chronic cough. Although gastroesophageal reflux disease (GERD), asthma, ACE inhibitor use, and post-nasal drip (upper airway cough syndrome) are the most common causes, there is no reliable test to identify the cause of chronic cough, and many patients do not respond to therapies for these conditions.