A comprehensive investigation including CBC, throat swab, allergic tests, X-rays, examination with a scope in throat
, spirometry etc is required keeping all the points in mind. A throat
swab and the phlegm should be given for culture and sensitivity to see what organism is causing the cough and what antibiotic may act against it. If it is viral or allergic then no culture will be formed. If it is due to air conditioning, you will have to use a humidifier.