I am extremely grateful to the person who made the suggestion of using wild organic oil of oregano under the tongue for constant coughing. Here is the suggestion, which I'd like to pass along:
Go to a health food store and get WILD MEDITERRANEAN OIL OF OREGANO. (there is a brand called Oreganol). It is very concentrated.
Place two drops under the tongue upon arising, at noon, and at nighttime. Keep it under your tongue for a minute or so, then swallow.
After trying all kinds of over-the-counter and prescription allergy pills and nose sprays, this has worked best for me.