Probably allergy but. See an allergist for a complete but simple evaluation. They can tell you the causes of your runny nose and give effective treatment. (even if turns out not to be "non-allergic" runny nose).
CSF? By far the most important thing for you is to be sure that this is not cerebrospinal fluid leaking through a tiny hole in the bottom of your skull. Your physician can determine this by using a urine dipstick to see if there is glucose in the fluid. This should be done as soon as you can. Good luck.