What causes post nasal drip after endoscopic sinus surgery?

Usually Allergies: Since you typically have more room in your nose after sinus surgery, pollens can now get to more of the nasal lining, sometimes making allergic drainage worse.

PND: Hello, your post op PND should be evaluated by your surgeon. It could be a normal mucosal reaction, allergy induced, leftover saline from irritations or a CSF leak. See your surgeon for confirmation.