A chronic cough is a cough that lasts eight weeks or longer in adults, or four weeks in children. A chronic cough is more than just an annoyance. A chronic cough can interrupt your sleep and leave you feeling exhausted. Severe cases of chronic cough can cause vomiting, lightheadedness and even rib fractures. While it can sometimes be difficult to pinpoint the problem that's triggering a chronic cough, the most common causes are tobacco use, postnasal drip, asthma and acid reflux.