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Clear Runny Nose: What’s Causing It?

A constantly runny nose can be triggered by a variety of causes—most of them not serious.
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Medically reviewed by
Last updated February 10, 2021

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Almost everyone has experienced a clear runny nose at some point in their lives. Also called rhinitis, a runny nose is your body’s way of responding to a whole host of triggers: infections, pollens, dust, spicy food, or even just cold weather.

The most common cause of a runny nose is the common cold. The cold virus triggers inflammation in the lining of the nose. The nose responds by producing discharge to try and clear the infection.

A chronically runny nose may be caused by sinus infections or allergies. Often, a clear runny nose can also be accompanied by other symptoms, like nasal congestion, sneezing, or itching.

Most of the time, a runny nose is harmless. It either goes away or you can take decongestants to slow the drip.

1. Common cold

Pro Tip

While a cold is a common cause of a runny nose, other conditions (like allergies) can also cause the same symptoms. If you’re experiencing any itching, that’s often a sign that you have allergies and not a cold. —Dr. Amrita Khokhar


  • Runny nose
  • Sneezing
  • Congestion
  • Post-nasal drip
  • Sore throat

The common cold is one of the most frequent causes of a runny nose. There are more than 200 viruses that can cause colds. Most children and adults get a few each year. Typically, a cold will resolve on its own without treatment.

Sometimes, the virus can cause inflammation in the sinuses, leading to sinusitis. Like a cold, you may have a runny nose and nasal congestion. But the drainage tends to be thicker and colored, and can cause facial pain.

Try nasal saline rinses to clear out mucus. Taking decongestants, for a short time, can help relieve stuffiness. Antibiotics aren’t needed to treat a cold—they aren’t effective against viruses.

2. Allergic rhinitis


  • Clear nasal discharge (runny nose)
  • Sneezing
  • Itchy, watery eyes
  • Itchy nose
  • Nasal congestion (stuffy nose)

Allergic rhinitis is another common cause of a clear runny nose. Allergens like dust, pollens, animal danders, and molds enter the nose and can stimulate the allergy cells that line the airway. These cells release several substances, such as histamine, that cause blood vessels to leak and produce the watery discharge—a runny nose. It’s often accompanied by sneezing and itchy, watery eyes.

There are two types of allergic rhinitis: seasonal allergies and perennial (year-round) allergies. Seasonal allergies are caused by pollens and molds that occur during certain times of the year. Year-round allergies are caused by triggers like dust or animal danders.

There are many treatments for allergies. You can do allergy testing to help identify what you’re allergic to. Then you can try to avoid the triggers.

When that’s not possible, medications can also help.

  • Over-the-counter nasal steroid sprays treat a runny nose and other allergy symptoms.
  • Over-the-counter and prescription antihistamines are used to help with sneezing and itching.
  • For more severe allergy sufferers, allergy shots may be used. They can help improve or sometimes even get rid of allergies.

Clear runny nose questionnaire

Use our free symptom checker to find out what's causing your clear runny nose.

Clear runny nose symptom checker

3. Non-allergic rhinitis

Dr. Rx

When your nose and sinuses produce mucus, it’s a defense mechanism—your nose is trying to protect you from the trigger, whether that’s an allergen or a virus. Tiny hair-like cells in the lining of your sinuses and the nose move mucus around in an attempt to capture and clear out these invaders. —Dr. Khokhar


  • Runny nose
  • Sneezing
  • Congestion
  • Postnasal drip

Nonallergic rhinitis is a broad term used to describe any kind of rhinitis that isn’t caused by allergies. The distinction is important, since allergies involve the immune system, while nonallergic rhinitis does not. If you have allergy-like symptoms, but your allergy testing is negative, you likely have a form of non-allergic rhinitis.

There are many causes of nonallergic rhinitis, though sometimes, a cause can’t be identified at all. Common causes include:

  • Cold weather
  • Exercise
  • Side effects of medications
  • Hormonal changes such as during pregnancy
  • Eating spicy foods
  • Pollution or smoke

In some cases, like in pregnancy, a runny nose will resolve on its own, while in other cases, you might need treatment if the symptoms continue to bother you. If your symptoms are occurring frequently, medications might be the next step.

Treatments include nasal steroid sprays, nasal antihistamine sprays, and a medication called ipratropium (which can help dry up mucus).

Other possible causes of clear runny nose

While a runny nose is typically a harmless condition, there are a few times when a runny nose might be a sign of something more serious:

  • Cerebrospinal fluid (CSF) leak: CSF is a watery fluid that surrounds and protects your brain and spinal cord. If the membrane holding the CSF in place is damaged, like after a head injury, it can drain into the nostril and appear like a runny nose. CSF leaks usually affect only one nostril, while other causes of a runny nose affect both equally. 
  • Autoimmune diseases: Autoimmune diseases occur when the immune system identifies the body’s own tissues as a threat, leading to inflammation. Some of these disorders involve the nose and the sinuses. One example is Churg-Strauss syndrome, which can lead to sinus inflammation. However, people with autoimmune diseases have multiple symptoms, not just a runny nose.

Clear runny nose questionnaire

Use our free symptom checker to find out what's causing your clear runny nose.

Clear runny nose symptom checker

When to call the doctor

Pro Tip

The most important thing you should tell your doctor is if you’ve been having any fevers, pain, or loss of smell. This can point to potentially more serious causes of a runny nose that should be investigated further. —Dr. Khokhar

A runny nose from a viral infection usually gets better on its own. However, if you start running a fever, notice colored or thick drainage, or your symptoms haven’t improved on their own, call your doctor. You might have a bacterial infection, which will need to be treated with antibiotics.

You may also want to see your doctor if you’re not sure what’s causing your runny nose. By discussing your history of symptoms and possibly being tested for allergies, you may be able to identify the cause.

If over-the-counter remedies aren’t working, the doctor can also discuss prescription options.

When to go to the ER for a clear runny nose

Call 911 or go directly to the ER if you have a severe headache with clear drainage from one nostril, especially after a head trauma. It could be a sign of a cerebrospinal fluid leak.


At-home care

The following treatments can help treat a runny nose, depending on its cause:

  • Saline sprays and rinses: If your runny nose is caused by a cold, a gentle saline spray or rinse can help flush excess mucus out of your nose and make it easier to breathe.
  • Nasal steroid sprays: These are first-line treatment for allergies. When used daily, they can help prevent a runny nose. Nasal sprays may also relieve sneezing and congestion.

Other treatment options

  • Antibiotics if you develop a bacterial infection.
  • Allergy testing, either through a skin prick test or blood test.
  • Prescription medications if over-the-counter options are not effective.
Hear what 1 other is saying
Clear fluid running nosePosted April 24, 2020 by P.
I'm usually ok during the night. Once I go down stairs to let the dogs out I'm still ok. As soon as I drink or eat something, within about 15-20 sec. later, my nose starts to run like a faucet. About 1/2 hour if I don't have anything to drink or eat I'm OK. Forget it at dinner time, I have to have a box of tissues with me. If I just have a drink of water when I'm thirsty or take my meds, I am OK. I'm constantly being told by my wife and daughters, "Your nose is running." At times you don't realize it, since the fluid is warm, until it cools off. Then you realize it.

Dr. Khokhar is a board-certified Allergist and Immunologist. She received her undergraduate degree in Biology from Stony Brook University in 2008 and graduated from the Renaissance School of Medicine at Stony Brook University in 2012. She completed a residency in Internal Medicine at Northwell Health in 2015, followed by a fellowship in Allergy and Immunology at the University of California, Irvine in 2017. She then spent two years as an attending physician in Allergy and Immunology at Tufts Medical Center in Boston, MA before moving back to her home state of New York. She recognizes the overwhelming obstacles in medical literacy and education that patients face while navigating healthcare, now the focus of her career. She joined Buoy as a medical writer in 2020.

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