Conclusion
Post-nasal drip is not life-threatening and usually resolves on its own. In cases where the symptoms persists for more than a few weeks, and a smelling and foul discharge accompanies it, with, difficulty breathing, or fever, you should see a healthcare professional to determine the cause.
Seek urgent medical attention if you have bumps on your face or persistent pain in your nose, lose or painful upper teeth, persistent or slimy cough with sore throat, white patches and redness on your tongue or mouth, persistent fever or sensation of something- something stuck in your throat that won’t go away.
References:
[1] https://www.webmd.com/allergies/features/the-truth-about-mucus
[2] https://www.mydr.com.au/respiratory-health/post-nasal-drip/
[3] https://www.medicalnewstoday.com/articles/319636#symptoms
[4] https://www.webmd.com/first-aid/coughs
[5] https://www.webmd.com/allergies/default.htm
[6] https://www.webmd.com/allergies/postnasal-drip#:~:text=However%2C%20green%20or%20yellow%20mucus,by%20sinusitis%20and%20viral%20infections.
[7] https://www.healthgrades.com/right-care/oral-health/throat-white-patches#:~:text=throat%20white%20patches%3F-,White%20patches%20at%20the%20back%20of%20your%20throat%20or%20on,associated%20with%20a%20syphilitic%20infection.
[8] https://www.cancerresearchuk.org/about-cancer/laryngeal-cancer/symptoms#:~:text=Post%20nasal%20drip%20means%20mucus,for%20more%20than%203%20weeks.
[9] https://www.webmd.com/allergies/postnasal-drip#:~:text=When%20your%20body%20produces%20more,throat%2C%20it’s%20called%20postnasal%20drip.
[10] https://medbroadcast.com/condition/getcondition/post-nasal-drip#:~:text=Symptoms%20and%20Complications&text=When%20allergies%20are%20responsible%20for,make%20breathing%20even%20more%20difficult.