Can postnasal drip cause dry mouth?

Absolutely can: The common oral symptoms of the postnasal drip are dry mouth and bad breath. Mouth breathing leads to a dry mouth (xerostomia) that leads to anaerobic bacterial growth due to an lack of saliva flow in the mouth. This problem needs a professional attention. Take care.

Postnasal Drip: Every day, glands in the linings of your nose make about a quart of mucus each day. The excess can come out of the nostrils -- that’s a runny nose. When the mucus runs down the back of your nose to your throat, it's called postnasal drip. http://www.webmd.com/allergies/postnasal-drip