What causes rid of a persistant cough?

Identify trigger. Rather than suppress a cough, it's best to identify the trigger of the cough so specific treatment can be given. The most common reasons for persistent cough are asthma, post nasal drip from allergies or sinus infections and acid reflux. There are many other less common causes. Typical evaluation for chronic cough includes chest x-ray, pulmonary function tests after a thorough history and exam.