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Cough for 3 months which is persisting needs complete evaluation by a doctor. First of all you may need a chest X ray
and blood tests to see for any infective organisms and allergies. Any sputum produced may also be tested for infective organisms. You have not written about any weight loss
therefore I consider you do not have the symptoms. Please stop smoking
as the smoke may contain irritants which cause inflammation of your respiratory tract
. Taking alcohol once a month can be allowed. Further you are advised to do salt water gargles twice a day for 15 days. Take precaution from cold weather exposure.
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Wishing you good health.