Does fenistil drops treat cough in babies.? my 3 month baby was prescribed 4 drops of this twice a day.. it's been only a day now , how long does it take to completely cure cough?

Cough is a protective mechanism at any age including young babies. It helps move mucus from deep to the outlet where it can be expelled. I NEVER give antihistamine drops for cough at that age as it thickens mucus & makes it harder to clear. Nasal saline suction to clear the nose, removal of any perfumes/irritants from their sleeping area helps. Cough stops when it is not needed.