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What Causes Post Nasal Drip?

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Updated October 05, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What Causes Post Nasal Drip?

Post-nasal drip is when you get mucus running down the back of your throat. Instead of coming out of your nostrils like a runny nose, the mucus drains from the nose into the back of the throat, forcing you to either swallow or cough it up. We constantly have mucus draining down the backs of our throats, but most of the time it is not noticed.

Anytime you can detect the mucous in the back of your throat, medical professionals refer to this as "post-nasal drip." Post-nasal drip can be accompanied by a sore throat even if it is not caused by an infection.

Answer:

The following are known causes of post-nasal drip:

  • allergies to pollen, mold, dust or dander
  • infections such as the common cold (CMV, RSV, adenovirus etc. . . ), influenza, sinusitis, swallowing disorders (may result in actual post-nasal drip or just cause the sensation of having post-nasal drip)
  • pregnancy or other conditions that result in a fluctuation of hormone levels
  • dehydration
  • eating spicy foods
  • eating too many dairy products, especially if you're not drinking enough water
  • low humidity in the air
  • certain medications like birth control and drugs that control blood pressure
  • foreign objects stuck in the nose
  • over-use of nasal sprays such as pseudoephedrine (for more information read: What Is Rebound Congestion?)
  • anatomical abnormalities such as a deviated septum or enlarged turbinates
  • acid reflux (GERD)
  • weather changes

Besides being a general annoyance, (causes constant swallowing, coughing and clearing the throat, laryngitis. . . ) post-nasal drip can also result in clogging of the auditory (Eustachian) tubes. This can lead to ear infections, so you should see a doctor if your post-nasal drip lasts more than a couple weeks or if it is followed by ear pain. In addition to being a direct cause of post-nasal drip, sinusitis (sinus infections) can be a complication of post-nasal drip because it can prevent your sinuses from draining properly. For more information about these conditions read:

Everything You Need to Know About Ear Infections

What Is Sinusitis?

Post-nasal drip is rarely an emergency, but you should get medical help if you are choking, drooling or unable to swallow.

Sources:

American Academy of Otolaryngology - Head and Neck Surgery. Post-Nasal Drip. Accessed: September 30, 2011 from http://www.entnet.org/HealthInformation/postNasalDrip.cfm

Medline Plus. Nasal Discharge. Accessed: September 30, 2011 from http://www.nlm.nih.gov/medlineplus/ency/article/003051.htm

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