I have a hacking cough for over two years now. i have asthma and am on inhalers, however if i lie horizontally the coughing stops. what 's up?

Cough gone on lying: Cough is a symptom of asthma and with "cough variant asthma" it is the only symptom. Asthma inhalers improve both types of asthma but if the cough isn't controlled then higher dose inhalers and other types of meds may be necessary. Usually lying down will make coughing worse so if it improves i would consult an ENT specialist to visualize your upper airway to rule out an anatomic cause.

Pedunculated polyp: A polyp or benign mass growing from a stalk above your vocal cords will hang down when you're standing irritating the true cords & causing cough. When lying down the polyp just hits the back of your throat or swings in the breeze, so to speak. Rare? Quite. Dr. Ostro is right this sounds like an anatomic problem requiring an ENT exam. A spirometry with flow-volume loop is also a good idea.