In a person who has a
normalNormal saline flush chest x-ray and who doesn’t smoke the most common causes of cough are postnasal drip, chronic sinus problem, heartburn, and asthma. A chronic cough can also be a side effect of a group of medicines used to treat high blood pressure called angiotensin converting enzyme (ACE) inhibitors. You need to be seen by your doctor and have testing done to figure out what this could be and the best treatment. It may be that you need treatment for your chronic lung disease.
One dose of Robitussin® a day is a harmless and small price to pay for cough relief.
An ENT could diagnose and advise. Link:
http://www.entnet.org/healthinfo/nose/nasal.cfm
Post-Nasal Drip
Excerpt:
"Allergy is managed by avoiding the cause if possible. Antihistamines and decongestants, cromolyn and steroid (cortisone type) nasal sprays, and other forms of steroids may offer relief. Immunotherapy (allergy shots) also may be helpful. However, some older, sedating antihistamines may dry and thicken post-nasal secretions even more; newer nonsedating antihistamines, available
by prescription only, do not have this effect. Decongestants can aggravate high blood pressure, heart, and thyroid disease. Steroid sprays generally may be used safely under medical supervision. Oral and injectable steroids rarely
produce serious complications in short-term use. Because significant side-effects can occur, steroids must be monitored carefully when used for more than one week. "