The nose is a surprisingly complex organ. It contributes to your sense of smell, hydrates and warms the air you inhale, and protects your body against harmful pathogens. Rhinitis is the medical term that describes inflammation of the nasal mucous lining, which can cause rhinorrhea -- a runny or stuffy nose.
Here are five things that can cause this common condition.
1. Cold temperatures
You may have noticed that your nose runs when you’re spending time in a cold room or doing outdoor activities on a cold day. This phenomenon happens for two reasons.
First, on cold days the air tends to be drier, so your nose produces more mucus to keep the mucus lining hydrated. The second reason your nose runs when you’re exposed to cold is because one of the functions of the nose is to warm inhaled air up to body temperature (which averages 98.6 degrees). The bigger the gap is between air temperature and body temperature, the more mucus your body produces in an effort to warm the air up as quickly as possible before it gets to your lungs.
2. Spicy Food
There’s a reason people say that eating spicy food “clears out your sinuses.” This is because spicy food triggers the trigeminal nerve, which innervates the eyes, ears, face and nose. When the trigeminal nerve is stimulated, it increases the amount of mucus the sinuses and nasal lining produce, causing you to sneeze and/or experience a runny nose. Rhinitis triggered by eating certain foods is called gustatory rhinitis.
Crying occurs when tears are produced by the lacrimal glands, which are located near your eyelids. The lacrimal glands are attached to the tear ducts, which drain into the nasal cavity. So, when you cry, tears mix with the mucus in your nose, which causes your nose to run.
Since your nose is one of the first lines of defenses against infections, it quickly senses when it’s been colonized with a harmful pathogen, such as the flu or one of the viruses that causes the common cold. When it senses it’s under attack, the body’s immune system releases T-cells and B-cells that fight the infection. These cells also stimulate the nose to increase mucus production in an attempt to literally drown the infection before it can replicate and spread.
Allergies occur when the body’s immune system treats a non-harmful substance (like pollen, dust or pet dander) as if it’s a harmful pathogen. Because the body’s immune system is designed to stimulate mucus production when it senses the presence of a harmful pathogen, the same mechanism is activated in patients who have allergies. Their immune system mistakenly reacts to a substance as if it’s capable of producing an infection and causes the nose to run.