I finally went to a specialist in Baltimore who read my history which showed all the meds I was taking and he noticed that I was taking Zetia and told me that he believed
Zetia caused chronic coughing in some people; so he looked
it up on his computer and sure enough, that was one of the warnings. I stopped the Zetia and the coughing disappeared completely within a couple of weeks. The point here is that medicines, while helping one problem, frequently can cause another.