It’s that time again: you’ve come down with a cold, you can’t stop sneezing, and your nose simply won’t stop running. Why does your nose run when you’re sick? It’s annoying, but biologically necessary.

I’m Sick. Why Won’t My Nose Stop Running?

You wake up with that old familiar tickle in your sinuses, and your mind immediately recoils in fear: you’re getting sick. Despite your best efforts, and all the work you did to try and stay healthy over the past several months, there was no avoiding it this time. You’ve got the common cold, and it comes with one particularly nasty and annoying symptom: your nose won’t stop running.

When your nose “runs”, it’s actually an overflow of your nose’s normal mucus production. You see, your nose does a lot more work than you probably give it credit for. All day long, as you breathe through your nostrils, your nose is busy warming, filtering, and modifying the air you’re breathing before it enters your body. This serves a variety of purposes, not the least of which is to filter out harmful pathogens before they can sneak in and get you sick. This job is primarily accomplished by your cilia (tiny hairs in your nose) and your nasal passage’s mucus lining.

Unfortunately, sometimes our noses (and by extension, our bodies’ immune system) allow a pathogen or two to slip through, and we become sick. One of the first signs that you’ve caught a cold is the telltale runny nose that seemingly won’t stop dripping — an annoying and icky feature, to be sure, but one that serves an important purpose. Believe it or not, a runny nose isn’t exactly a symptom of what the cold is doing to you so much as it’s evidence that your body is working to fight the cold off.

The Miracle Of Our Immune System

Your body’s immune system is like a police force for your health, actively tracking down and removing threats to your wellness. When something bad (a pathogen) enters the body, your immune system recognizes it quickly and begins doing the work of ridding it from your system. Of course, sometimes your immune system gets a little overzealous, as in the case of allergies, but usually its response is necessary and appropriate to the foreign threat it detects.

In the case of a cold, one of the ways your body works to eliminate it is by sending your nose’s mucus lining into a frenzy in an attempt to shed any harmful bacteria or viruses living in there. Protein messengers in the body are so good at swelling your mucus lining to elicit this response, that excess fluid can build up to some pretty incredible (and gross) levels. Hence, a runny nose.

So, the next time you’re sick and you can’t stop blowing your nose, try to keep one thing in mind: a runny nose isn’t a cold, per se. It’s your body’s natural and healthy way of shedding that cold as fast as possible so you can feel back to normal in a few days.