It could be a side affect of blood pressure meds. I had the same problem when I was on lisinipril, when they changed
my meds, I have not had the problem since.
If anyone in your family (household) takes Lisinopril for blood pressure, that is probably the culptrit. I took it
for two years and caughed constantly. I've now been off it for a year and caugh from allergies. My doctor also
gave me a nasal spray to use at night to open he air waves. this also helped. Good luck.
Neti pots are inexpensive and can be purchased at drug stores, Wal-Mart, even some local potters make them. They look
like a combination of a cup and tea pot and hold about 8 ounces of water. I started using one a few years ago when
seasonal allergies became significant.
You can find more information here: Web MD - Nasal Saline Irrigation and Neti Pots