I usually give him 1 to 2 L'il Critters gummy vites that have Echinacea, Vitamin C, and Zinc in them every day. He doesn't cough during the day. He had a cold a few weeks ago, which has since gone away, except for this cough. It actually starts late in the evening right around bedtime, continues off and on during the night when he changes positions, and then starts to go away around mid-morning.
I would say it's probably more of a dry, hacking cough. Could it be whooping cough?