I have had almost constant sinus drainage for over 25 years. I have been to mutliple physicians and have been told my sinuses are fine. I have no allergies or infection. It doesnt matter what season it is or the temperature or the humidity. I do not get headaches from it. It runs down the back of my throat and is very watery coming out of my nose.  I blow my nose almost every half hour or more. I took nasal Atrovent for 10 years, but I started to get a bad cough from it going down the back of my throat, so I stopped. It is very difficult to work and have to worry about my nose dripping at almost any time. Can you think of any other situation that could be causing it?
Thanks for asking in Chat Doctor forum. In Short: Visit a ENT specialist when you are having the problem. Explanation: Don't lose your heart, be patient. Continuous post nasal Chat Doctor.  So it is better to visit a ENT specialist when you are suffering from this condition.  Any discharge from nose usually