A woman deals with a runny nose

Runny Nose Causes

Having a runny nose, or rhinitis, is the result of excess drainage that can take the form of clear fluid or thick mucus that is produced by the nasal tissues. Runny nose drainage can run out of your nose or down the back of your throat, or sometimes both. There are various potential causes for having a runny nose. Here are some of the most common ones. 

Viral Infection

The common cold is the most common cause of a runny nose, since there are over 100 different viruses that can cause it. Unfortunately, there is not much you can do to treat the common cold, other than rest and wait for it to run its course.

The flu is also caused by a virus that attacks your throat, lungs, and nose. A runny nose is usually the least of your problems if you have the flu, since it causes many other symptoms such as nausea, vomiting, fever, aches, and fatigue.

The reason nasal discharge occurs when you are sick with a viral infection, such as the common cold or the flu, is because your body begins making extra mucus in an attempt to trap the virus before it is able to make its way to your lungs. Some of this excess mucus will make its way out of your body through your nose, resulting in a runny nose.


Similarly to how your body responds to a viral infection, your body reacts to allergens as though they are harmful bacteria, which also causes your nose to run. Common allergens include dust, pet hair, and grass. If you are allergic to any of these allergens, you will likely experience nasal discharge whenever you touch or inhale the substance.


Sinusitis is a condition that occurs when the passages of your nose (sinuses) become inflamed and swollen. This results in a narrowing of the nasal passages which can lead to difficulties breathing and a buildup of mucus. Mucus that is associated with sinusitis is usually very thick with a green or yellow hue. It can drain out of your nose, but it also might drain down the back of your throat, causing you to cough it up.

Other Causes

There are many other conditions that can also cause a runny nose to develop. A few other causes of runny nose include:

  • Pregnancy: It’s common to feel congested during pregnancy. The elevated amounts of estrogen when you are pregnant can cause swelling in the mucous membranes, which cause your body to produce more mucus than normal.
  • Cluster headache: This is a rare type of headache that can be extremely painful. Among other symptoms, one of the common things associated with cluster headaches is a blocked or runny nose.
  • Drug addiction: One of the signs and symptoms that someone might be snorting an illegal substance is a runny nose or sores in the nose.  
  • Nasal polyps: Nasal polyps are painless, noncancerous growths that can form on the lining of your nasal passages. If the polyps grow large enough, they can cause symptoms such as difficulty breathing and runny nose.
  • Hay fever: This is a condition that causes cold-like symptoms, including runny nose. However, unlike the common cold, hay fever is not causes by a virus. Instead, it is an allergic response to allergens such as pollen, dust mites, or pet dander. 
Last Updated: December 01, 2016