Zyrtec-D = Horrible Dry Mouth I was only able to stay on Zytec-D for a few months. The side effect I noticed the most was the residual dry mouth and throat. Drinking water and sucking on hard candies could not relieve the discomfort. I would couging uncontrollably during meetings, was very uncomfortable and felt that I had terrible breath (confirmed by my fiance) because there was no saliva in my mouth to wash away bacteria.