Coughing is a reflex that keeps your throat and airways clear. Although it can be annoying, coughing helps your body heal or protect itself. Coughs can be either acute or chronic. Acute coughs begin suddenly and usually last no more than 2 to 3 weeks. Acute coughs are the kind you most often get with a cold, flu or acute bronchitis. Chronic coughs last longer than 2 to 3 weeks. Causes of a chronic cough include chronic bronchitis, asthma, allergies, GERD, smoking, COPD and related lung conditions and some medication can also cause cough.