Persistent cough

I have a 9yo boy who has a persistent cough. It happens at odd intervals, but most often after exercise or activity. He has been to several doctors, but they have found nothing to suggest anything other than a mild cold.

However, this cough doesnt appear to be linked to asthma, because he doesn't have the typical restricted breathing of the asthmatic.

Rather, this cough seems to be a phlegmmy cough.

Any suggetions? Tweet