A runny nose, also known as rhinorrhea or rhinitis, occurs in most people when they are suffering from a cold. There are many other causes, however. Your nose runs because the blood vessels and tissues in your nasal passages become swollen or congested. If there is more than the usual amount of liquid or mucous, it will come out through the nose or drain into the throat.
Cold and Flu
Typically, the infection that causes you to get influenza or a common cold triggers a runny nose. This type of mucus flow typically will be more green or yellow in color than that of allergies or other triggering causes or materials. These infections also cause fever, chills, nasal congestion, diarrhea and throat soreness. The Mayo Clinic notes you may get a runny nose whether you are congested or not.
Irritants
Many irritants in the air around you can cause your nose to run. For example, if someone is smoking near you and you inhale the fumes, this could trigger rhinorrhea. Other substances that irritate your mucus membranes such as paint fumes, nail polish remover and decaying garbage, also may trigger a runny nose.
Sinusitis
Sinusitis comes in two forms, acute and chronic. It essentially is an inflammation and swelling of your sinuses or nasal passages. The acute form typically occurs when you have a cold or flu. The chronic form may be caused by nasal polyps, which are sinus growths, by an infection or by having a condition known as a deviated nasal septum, the Mayo Clinic reports. Both conditions cause difficulty breathing through the nose as well as rhinitis.
Bronchiolitis
Viruses typically cause this condition, which is an airway infection in the lungs. This condition is more common in infants ages 3 to 6 months than in older children or adults. This infection can trigger the same effects as the flu and make the child's nose runny. In most cases, the Mayo Clinic reports, bronchiolitis is not serious. It may become so, however, if there is some other health problem with the child, particularly a problem with the immune system. In most babies, the problem will continue no longer than a week.
Allergies
Along with colds, allergies may start the swelling and congestion in your nasal blood vessels and tissues. Some of the most common allergens that cause a runny nose include wheat allergies, soy allergies, shellfish allergies, latex allergy, hay fever and pet allergies, as well as dust and pollen.
Measles and Chickenpox
Both of these childhood diseases can start a bout of rhinorrhea. Both are quite contagious, but neither are serious in most cases. They are infections that typically last a few weeks before passing and not returning.
Spicy Foods
You may ingest other irritants that can cause your nose to run, too, such as foods that are too spicy. In particular, foods that include as an ingredient capsaicin, a chemical, can make your nose run because the substance is an irritant that creates nerve inflammation and increases the amount of mucus produced. Capsaicin is found in many spicy foods, such as anything made with chili peppers.
