Talk to Ent Specialist on Dry Cough

I've consulted with chest specialist in Chiniot General Hospital Karachi. I have disclosed him my chest xray and lungs test. He told me that all clear and there is no issue, you have only alergy and he suggest me softine tablets 2 a day and vintoline inhelar of GSK company. I'm following his advice and still no effect. Still I have cough.

Further more I have stomach problem and then after 2 days of consulting with chest I go to gestro specilaistes in the same hospital he give me omezol, motalium and speghool, and he called me after 4 weeks then he will do my endoscopy and a blood test.

What is alergy and how do i find that from which things i have alergy? I can't find it myself because i live in ac rooms, i live in without ac rooms, i drive my car with ac and without ac, what is it actually?