Possible Causes of Post Nasal Drip

The main symptom of post nasal drip is the feeling of having phlegm in the back of your throat. There are several different conditions which can result in the same symptom, and determining the cause is the best way to make sure you receive the best treatments.

Man suffering from post-nasal drip
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Causes of Post Nasal Drip

Post-nasal drip can be caused by allergies, among other things. There are many causes of post nasal drip, or phlegm in the throat, which causes many people to frequently clear their throats. While the symptoms are similar, causes may include:

  • Allergic rhinitis (hayfever)
  • Non-allergic rhinitis (vasomotor rhinitis)
  • Sinusitis
  • Gastroesophageal reflux disease (GERD)
  • Hormonal causes such as pregnancy or hypothyroidism
  • Overuse of nasal sprays such as Afrin

Allergic Rhinitis as a Cause of Post Nasal Drip

Post nasal drip may be a symptom of allergic rhinitis (hayfever) although it’s quite uncommon to have post nasal drip as the only symptom. Typically, allergic rhinitis symptoms also include sneezing, nasal congestion, and a runny, itchy nose.

People with post nasal drip caused by allergic rhinitis are diagnosed in much the same way as those with other types of symptoms. Positive results on allergy testing suggest that there is an allergic cause to the symptoms. Having a good response to treatment with medicines for allergic rhinitis also increases the chance that post nasal drip is related to hayfever.

Non-Allergic Rhinitis as a Cause of Post Nasal Drip

Post nasal drip may also be caused by non-allergic rhinitis, or vasomotor, rhinitis. A non-allergic cause may be suspected in an older person with post nasal drip symptoms who did not have problems with allergies when he was younger.

Non-allergic triggers of post nasal drip may include worsening symptoms with weather changes, exposure to strong odors or perfumes, eating spicy foods (gustatory rhinitis) or as a result of taking various medicines for high blood pressure (medication induced rhinitis). Non-allergic rhinitis may also be worsened by sex and by exercise (exercise-induced rhinitis). By definition, people with non-allergic rhinitis show no reactions to allergy testing.

Treatments for non-allergic post nasal drip include nasal steroids, nasal antihistamines, anticholinergic nasal sprays (such as ipratropium bromide) and older oral antihistamines, such as Benadryl (diphenhydramine) or Chlor-Trimeton (chlorpheniramine), used for their drying side effects.

Sinusitis as a Cause of Post Nasal Drip

Post nasal drip may also be the only symptom of sinusitis (infectious rhinitis), or it may go along with other symptoms, such as facial pain, nasal congestion, and colored nasal discharge. When post nasal drip is the only symptom of a sinus infection, it is usually because the infection is a low-grade “smoldering” infection that has been going on for months, and sometimes even for years. Because the symptoms of these types of sinus infections are so mild, a diagnosis is often only made after a CT scan is performed.

Post nasal drip caused by a sinus infection is treated with antibiotics, although the antibiotics may need to be taken for a longer period of time if the infection is thought to be chronic (lasting for more than two months or an infection that keeps coming back).

Gastroesophageal Reflux Disease as a Cause of Post Nasal Drip

While gastroesophageal reflux disease (GERD) does not cause post nasal drip, it may mimic the symptom. Accompanying symptoms of GERD may include heartburn, chest discomfort, or abdominal pain. The diagnosis of GERD may be made using direct laryngoscopy, which may show irritation in the upper throat from stomach acid; with a 24-hour pH probe; or with esophagogastroduodenoscopy.

The treatment of GERD most commonly includes the use of proton pump inhibitors for many months. What many people do not realize is that there can be serious complications of long-term untreated GERD. Not only does having reflux affect your quality of life, but can cause esophageal erosions, and though much less common, esophageal cancer.

Rhinitis Medicamentosa

Rhinitis medicamentosa is a complicated way to describe the type of a runny nose and congestion which occurs when a person has been over-using a medication like Afrin (oxymetazoline). As the body adapts the medication, more and more of the medication is needed, and severe post nasal drip may occur until the cycle is broken.

Pregnancy as a Cause of Post Nasal Drip

Pregnancy-induced rhinitis or hormonal rhinitis is a common cause of post nasal drip in pregnant women. Symptoms usually begin during the second trimester and persist until delivery, with symptoms resolving shortly after the baby is born. For some women, hormonal rhinitis may occur with the use of birth control pills or when thyroid function is low (hypothyroidism.)

Evaluating the Possible Causes of Post Nasal Drip

As noted above, there are many causes of post nasal drip which go far beyond allergic rhinitis alone. Some of these causes may be separated out with a careful history, such as the age of the person, time of year, time of day at which the drainage occurs, other symptoms, and response to treatments which have been tried. The examination can also be helpful in looking at the consistency of the drainage (thinner with allergic and non-allergic rhinitis and often thicker with sinusitis.)

While these causes can overlap, it's important to work with your doctor so that you can come up with the best treatment possible. Post nasal drip, while it is not a life-threatening symptom, can impact your quality of life as well as a performance at work or school.

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Additional Reading
  • Kasper, Dennis L.., Anthony S. Fauci, and Stephen L.. Hauser. Harrison's Principles of Internal Medicine. New York: Mc Graw-Hill Education, 2015. Print.
  • Kliegman, Robert M., Bonita Stanton, St Geme III Joseph W., Nina Felice. Schor, Richard E. Behrman, and Waldo E. Nelson. Nelson Textbook of Pediatrics. 20th Edition. Philadelphia, PA: Elsevier, 2015. Print.
  • U.S. National Library of Medicine. Medline Plus. Allergic Rhinitis. Updated 05/09/17.