Hello! Thank you for being with Health Care Magic. Thats a very good question becausing cough is one of the most common complaints we get in practice. Cough is a reflex reaction of our body to certain triggers that can cause irritation to our airway. triggers can be inhaled dust particles, excessive secretions or inflammation of the airway secondary to infection or an allergic component. It is very important to note the quality of the cough, when does it usually occur, or if with fever to be able to give the proper management. Cough can be dry because of too little phlegm or it is too sticky. The cough syrup that you gave your child loosened the phlegm which is why you hear the wet cough. Cough medicines mainly try to suppress it but does not treat the underlying cause. It is best to go back to your doctor so she can perform a complete physical examination on your child. Hope I was able to answer your question.