See a doctor, in some areas Pertussis is going around. Try steam, run the hot water in the bathroom and let the steam build up and see if that helps. Sometimes sipping cold or warm water. There is a medication called, Perls that you can get a prescription for that you swallow and it numbs the throat so the tickle feels better for a while.
I know it is hard to listen to someone cough but he really should be seen to rule out something more serious and contagious.