The Difference Between a Runny Nose and a CSF Leak

When a lot of fluid drips from your nose

Cerebrospinal fluid (CSF) rhinorrhea is different from a typical runny nose because it causes continuous dripping out of one nostril. This rare condition happens when fluid surrounding the brain leaks through the nose. You may be able to tell if you have a CSF leak by the way your nose is draining.

Most often, a runny nose is caused by allergies, the common cold, or cold weather. CSF rhinorrhea can be caused by an injury or a surgical complication.

This article discusses the causes, symptoms, and treatment of CSF rhinorrhea. It also explains how you can tell the difference between a common runny nose and a CSF leak.

A woman blowing nose with a handkerchief
Eugenio Marongiu / Getty Images

How to Tell If You Have a Runny Nose or CSF Leak

Symptoms of CSF rhinorrhea include:

  • Clear thin liquid running from the nose
  • Drainage that increases while leaning forward with the head down
  • Runny nose that gets worse with a change in position (such as standing up or bending down) or after performing the Valsalva maneuver (when you pinch your nose, close your mouth, and attempt to exhale)
  • Salty or metallic taste in the mouth, due to the contents of the cerebrospinal fluid
  • Lack of smell (anosmia)
  • Headaches and fatigue

What Causes a CSF Leak?

The brain and spine are surrounded by cerebrospinal fluid. This fluid is contained by connective tissue called the dura mater.

When there is a tear or hole in the dura mater of the brain, it is known as a cranial CSF leak. This causes CSF to leak into the sinuses (two sets of cavities in your head) and out through the nose. This is different from a spinal CSF leak, in which the fluid leaks from the spine and does not cause nasal symptoms.

Causes of CSF rhinorrhea include:

Between 80% and 90% of CSF leaks in adults are due to traumatic brain injuries.

Differences Between a Runny Nose and a CSF Leak

Runny Nose
  • Nasal discharge can be thick or thin, colored, or clear

  • Nasal discharge comes out of both nostrils

  • Usually improves with cold or allergy medications

  • Does not typically cause loss of smell

CSF Leak
  • Nasal discharge is thin and clear

  • Nasal discharge may come out of only one nostril

  • Does not improve with cold or allergy medications

  • Can cause loss of smell


With CSF rhinorrhea, bacteria can spread from within the nasal passages and sinuses through the hole in the dura and into the lining around the brain.

This can cause bacterial meningitis, a life-threatening infection.

Testing to Diagnose a CSF Leak

While CSF rhinorrhea is a rare condition, if you have a chronic runny nose without other symptoms of nasal allergies (allergic rhinitis), such as sneezing, nasal congestion, and watery eyes, you may need to be evaluated for the condition.

Anyone who has had repeated episodes of bacterial meningitis should also be evaluated.

Tests use to diagnose a CSF leak include:

  • Sample testing: Collecting some of the nasal discharge and testing it for a protein called beta-2 transferrin, which is only found in cerebrospinal fluid.
  • Pledget study: With this, small cotton pads called pledgets are placed in the nose to identify the presence of CSF.
  • Imaging tests: Computed tomography (CT) and magnetic resonance imaging (MRI) scans may help determine the location and severity of the leakage.

Treating a CSF Leak

Once the site of the CSF leak is located, it can be surgically corrected using a number of different techniques.

Most commonly, a CSF leak is fixed with a minimally invasive nasal endoscopy and grafting procedure and will resolve within seven to 10 days.

A surgeon inserts a flexible tool with a light and camera into a nostril in order to see inside. While viewing the affected area on a monitor, they patch it using a graft. The graft can either be artificial tissue or a piece of your own tissue or fat.


Cerebrospinal (CSF) rhinorrhea is a rare condition in which spinal fluid leaks from a tear in the meninges into the sinuses and nasal passages.

CSF rhinorrhea is different from a runny nose caused by a cold or allergies. The fluid is always thin and clear, and symptoms don't improve with cold or allergy medicines.

Once a CSF leak is diagnosed, a surgeon can perform a procedure to repair the tear.

If you're experiencing a runny nose without other allergy symptoms, or a runny nose that doesn't get better with time or with allergy medication, ask your healthcare provider if you should be evaluated for a CSF leak. This is especially important if you had a head injury before a runny nose started or if you have ever contracted meningitis.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Cedars-Sinai. Cerebrospinal fluid leak.

  3. Oh JW, Kim SH, Whang K. Traumatic cerebrospinal fluid leak: Diagnosis and managementKorean J Neurotrauma. 2017 Oct;13(2):63-67. doi:10.13004/kjnt.2017.13.2.63

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By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.