I apologize for not reading the responses to see if someone already suggested this, but I had a cough like that last year, that I swear felt like I had for months! Then one day I was out with friends and I ate some nachos with a hidden jalapeno pepper in it. I bit the pepper and it was so hot... but at the same time I KNEW right then it had worked a miracle. And it did! After that I went and bought a jar for the frig, and when I get a nagging cough I just put one on a cracker with some cheese, bite right in, and voila.... cured!
I don’t think anyone else has suggested that, although I might have missed it. I bet it would work on certain coughs, and I’m going to try it the next time I get one.