I was curious how to tell if you have a cough from post-nasal drip vs. a real sinus infection or does it matter? My daughter gets the usual winter colds and it seems once she starts coughing from post-nasal drip she usually doesn't stop til we put her on antibiotics. She keeps getting colds and now she has yet another one, the drippy nose is settling down but she does have a cough during the day from the cold. the stuff draining from her is clear, but it usually is clear and even when she's needed anti in the past . anyway, we're seeing her CF doc in 2 weeks and if she doesn't get better of course I'll call sooner but I hate calling for every cough /cold even though it makes me worry.