Thanks for coming to HCM.
chronic cough as per definition is cough more than eight weeks. The possible causes can be:
1)Cough variant asthma
which can be ruled out by bronchial provocation test,
where pulmonary function test is normal but there is raised sputum eosinophil and can be readily made out by sputum microscopy.
3) 10% of hypertensive patients who are on ACE inhibitors group of drugs like ramipril, enalapril etc. Cough subsides on discontinuation of drug.
, pharyngitis, rhinitis via a mechanism called post nasal drip
, where the secretion trickle down in trachea and cause cough.
5) Gastroesophageal reflux disease
(GERD) by trickling of refluxed acid into the trachea and causing inflammation.
6) Parasitic infection
of the lung like tropical pulmonary eosinophilia
in filariasis. But here blood eosinophilia is there and you said blood test is normal, so ruled out.
7) Any chronic disease like bronchictasis, tuberculosis, cancers etc but these are readily catched on CT scan.
In your case, you must have provided your history in these context and gone for respective examinations. I can understand your concern. Many a times cough is so irritating and exhausting. Meet pulmonologist with proper history concerning the above points to reach a specific diagnosis..