What can do or what type of medication should i take for my cough that i have had for about a month?

Cough: The 4 main causes of persistent cough are asthma, post nasal drip from allergies or sinus infection and stomach acid reflux. A lingering cough may occur after the "flu" or other viral respiratory illness. A lingering cough may be due to whooping cough (pertussis). There are many more less common possibilities. To effectively treat, it is important to have right diagnosis-see lung specialist.