Runny Nose Causes, Treatments, and Prevention

You probably have had a runny nose at some point in your life. So, you know how annoying it can be to have a tissue within close reach at all times. 

But what you may not be familiar with is what exactly happens when your body continuously produces that nasal liquid, known medically as rhinitis. For starters, knowing that a "runny nose" is excess mucus dripping out of your nostrils is important. The discharge can be thin or thick and has a range of colors, from clear to yellowish to greenish.

Also, that excess mucus can drain down the back of the throat, called post-nasal drip, which sometimes accompanies a runny nose.

There are several causes for a runny nose. Here are some of the most common viruses, environmental triggers, and health conditions that can trigger a runny nose and how to stop that excess mucus.

What Causes a Runny Nose

A runny nose usually occurs when the tissues lining the nose become swollen from inflamed blood vessels. There are many causes of a runny nose, ranging from mild to serious ones.

Here are some common causes of a runny nose, including one possibly unknown cause you should know about.

Temperature

Your nose helps filter, humidify, and warm the air into your lungs. That happens through a system that includes:

• Mucosa: The moist tissue that lines the inside of your nose
• Mucus: The sticky solution that traps bacteria and viruses
• Cilia: The tiny hairs that move trapped particles and mucus to the back of your throat

When it's cold out, dry air makes the nose work extra hard to add fluid. The excess fluid drips out of your nose.

Common Viral Infections

You might get a runny nose if a virus enters your body and causes an illness. Some common viral illnesses that cause a runny nose include:

• Common cold: A runny nose is a hallmark symptom of the common cold. Essentially, your nose tries to fight off the germs by increasing mucus production, which then drips out of your nose.
• Flu: Similar to a common cold, your nasal tissues become irritated when you have the flu, leading to a runny nose.
• Respiratory syncytial virus (RSV): This infection can also cause a similar reaction to the common cold and flu.

Allergies

Your body's response to allergies is similar to how it reacts when you have a viral infection. Essentially, your body makes more mucus to get rid of the invader: the allergen. 

The allergen triggers the immune system to send immune cells to wherever the allergen is, which opens the blood vessels. That response causes nasal congestion and extra mucus production.

Sinusitis

Sinusitis, commonly known as a sinus infection, happens when the tissue that lines your sinuses becomes inflamed or swollen. A sinus infection interferes with your mucus drainage, causing it to build up. The discharge that comes with a sinus infection is usually thick, yellow, or greenish mucus.

COVID-19

The Centers for Disease Control and Prevention (CDC) lists runny nose as one of the main symptoms of COVID-19, a disease caused by the virus SARS-CoV-2. As with other viral infections, with COVID-19, your body tries to prevent the virus from entering the body.

Overuse of Nasal Spray Decongestants

Nasal spray decongestants can help relieve stuffiness. But using them too much can cause what's known as a rebound effect, where they make your symptoms worse.

"Nasal decongestants help to shrink or constrict blood vessels in the nose, which helps to decrease the sensation of nasal congestion," Sophia Tolliver, MD, MPH, a clinical assistant professor of family medicine at The Ohio State University Wexner Medical Center, told Health. "As the vessels shrink, blood and nutrients are squeezed out."

But once the medication wears off, the blood vessels become swollen again, leading to more congestion and runny nose symptoms.

Cerebrospinal Fluid Leak

Cerebrospinal fluid (CSF) leaks don't happen often. Still, it's a good idea to have it on your radar since there can be complications if untreated. 

CSF is the cushion surrounding your brain and spinal cord to protect them from injury. In rare situations, CSF can leak into the spinal column or the skull. 

A runny nose can be a symptom of the latter, a cranial CSF leak. That typically involves a watery-looking discharge that usually comes out of one nostril and a metallic taste in the back of your throat, said Dr. Tolliver. 

Treatment

The exact treatment for a runny nose ultimately depends on the underlying cause. Most of the time, a runny nose just has to run its course.

But if you want to do something to feel better until things clear up, you can try the following tricks:

• Drink plenty of water: Staying well-hydrated can help keep your mucus thin, "which will help it drain faster," said Dr. Tolliver.
• Use over-the-counter (OTC) nasal steroids: These can be helpful if you suspect or know that your runny nose is due to allergies. They come with some side effects, however, so it's important to read the information on the box to determine if they're the best choice for you.
• Do a saline rinse: This is also known as nasal irrigation. Using a tool like a Neti Pot can help to flush out mucus and irritants.
• Use a nasal mist: This is easier and quicker than nasal irrigation. Spritzing a saline mist into your nose can help moisten your nasal passages and clear out allergens that could be lurking in there, said Dr. Tolliver.
• Run a humidifier at night: A cool mist humidifier will help keep nasal passages moist. A humidifier can also help drain mucus from your nose more quickly than normal.

How To Prevent a Runny Nose

There are certain runny nose causes, like being out in the cold, that you can only do so much about. But when it comes to viral illnesses, there are a few ways to prevent a runny nose, including:

• Washing your hands often with water and soap (or use hand sanitizer in a pinch) for at least 20 seconds
• Avoiding touching your eyes, nose, and mouth with unwashed hands
• Staying away from people who are sick
• Wearing a mask that fits properly
• Staying up to date with vaccinations
• Keeping your immune system healthy by eating a balanced diet, exercising regularly, and getting adequate sleep

If allergies usually cause your runny nose, the American College of Allergy, Asthma & Immunology recommends avoiding areas that will trigger your allergic reaction. You may also want to use OTC antihistamines or nasal steroid sprays to help manage your symptoms before they start.

When To Contact a Healthcare Provider

If you develop a runny nose here and there, there's nothing to worry about. But there are a few different situations where you'd want to seek medical care for a runny nose, including:

• Your discharge from the nose has a bad smell.
• Only one nostril is runny.
• Your nasal discharge is a color other than clear, white, or yellowish.
• Your runny nose follows a head injury.
• You have a fever in addition to a runny nose.
• You have a sore throat or white or yellow spots on the throat or tonsils and a runny nose.
• You have symptoms that last for more than three weeks.
• Your runny nose is accompanied by blurred vision or swelling on any part of the face.

A Quick Review

A runny nose happens when mucus continuously drains out of your nostrils, typically when the tissues lining the nose become swollen from inflamed blood vessels. Anything from allergies to the common cold can cause a runny nose. Most of the time, a runny nose just needs to run its course. 

In some cases, a runny nose may require medical intervention. Consult a healthcare provider if only one side of the nose is runny or other symptoms, such as blurred vision or white or yellow spots on the throat, accompany your runny nose.