Brief Answer: most common causes are post nasal drip, gerd,asthm Detailed Answer: HI, thanks for using healthcare magic Cough can be related to a reaction to irritation that occurs anywhere from the pharynx (back of the throat) to the lungs. A cough can be classified as acute ( lasting less than 3 weeks ), subacute (from 3 to 8 weeks) or chronic cough (lasting longer than 8 weeks). The most common cause for an acute cough would be a respiratory tract infection such as the common cold. The most common reasons for a persistent cough are post nasal drip , GERD (gastroesophageal reflux disease) and asthma. Post nasal drip is the more common out of these three.Some persons may have 'silent post nasal' drip where they do not have alot of other symptoms except the cough.The other symptoms that can be associated with post nasal drip are sore throat, clearing of the throat, nasal congestion , sneezing. Gastroesophageal reflux can also cause a cough due to the acid irritating the pharynx. Again the typical symptoms of reflux may not be present and the person may present only with the cough In terms of the asthma , you have indicated that you have been evaluated for this. Because post nasal drip is the most common cause treatment is generally aimed at this first. This means the use of a topical nasal spray, a decongestant and antihistamine. Examples of nasal sprays are nasonex, nasocort, rhinocort , flonase. This treatment should be continued for at least 3 weeks to 1 month to determine if this is effective. If there is no response then reflux medication can be started. I hope this helps, feel free to ask any other questions

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