Every time I get bouts of pnd and cough, it can last for months and nothing cures it, except swigs of Black cumin seed oil will quiet the cough for a few hours. Then I discovered the cure! Catch a common cold! At the end of the cold, after about 5-6 days of snot running buckets, the whole mess with the pnd and cough goes away! It’s happened enuf times that its not a coincidence, it works! I don’t suppress the snot faucet with NyQuil or the likes, just let it empty.