How do you treat a post nasal drip chronic cough/ no runny nose in a 6 year old. Have been giving Claritin and Flonase for 3 months with no relief.?

Depends. ARe you sure the chronic cough is due to post nasal drip? It could be caused by asthma or reflux. Also you may not be using the Flonase properly, make sure it is pointed outward toward ear and use consistently on a daily basis. Claritin might not be strong enough antihistamine. Have child checked by pediatrician or allergist.