When you have a cold, your nose will run a lot, but how much? Science is strangely silent
A runny nose is one way your immune system is trying to clear the virus, but just how much of a runny nose you have when you’re sick is a murky question.
When we’re sick, our noses often feel like mucus-spewing machines.
When you’re suffering from a cold, your nose feels like it’s constantly running, and you use countless tissues to wipe away the bright yellow chunks of booger and runny mucus, resulting in mountains of used tissues piling up.
And as you try to comfort yourself with hot soups and over-the-counter medicines (most of which don’t do anything), a question comes to mind: How much mucus do people actually produce when they have a cold?
It should hold at least one coffee cup. Maybe a sink? Or a car? I bet someone tried to measure it for sinus science.
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As it turns out, it was just a handful of brave scientists who collected tissues for the common good, and based on what these intrepid researchers have discovered so far, the amount of mucus produced by our heroic struggles with the virus may not be as much as we thought.
Mucus plays a surprising number of useful roles in the human body, from lining the intestinal tract and making stool sticky to acting as a natural lubricant for vaginal sex. The slick mixture of water, salts, and gel-forming proteins called mucins that make up mucus also helps trap dust, allergens, and infectious particles in the nose, mouth, trachea, and lungs. This sticky mucus and clotted mass of unwanted particles is then swept up with the help of tiny hair-like structures called cilia and dumped into the back of the throat, where it is usually swallowed, hopefully unnoticed (until someone points out that it does. You’re welcome). Overall, even when you’re not suffering from a cold, your body produces a fair amount of mucus, over 1.5 liters a day. Even if you’re not sick, you’re still swallowing the equivalent of a large ice cream tub of snot every day.
But when you have a cold, it can feel like your nose is running wild. When you’re sick, mucus doubles as your primary immune response, mainly due to its sticky nature, leading to excessive booger production. Blood flow rushes into the nose, causing nasal tissue to swell and make breathing difficult (that’s why it’s hard to breathe no matter how much you blow). Submucosal glands and cells called goblet cells pump out chunks of mucus proteins, which fill with water, and the resulting overflow is expelled in a tsunami of mucus, hopefully flushing out harmful virus particles in the process.
But finding out exactly how much mucus a cold produces is a tricky question, because there are so many variables at play. There are at least 160 different rhinoviruses that cause the condition we call the common cold, and each one triggers a slightly different immune response. And other viruses, such as coronaviruses and respiratory syncytial viruses, can also cause a variety of cold-like symptoms. Different people are known to respond differently to the same infection. Some viruses are very mucus-rich, while others remain relatively dry. People who live in dry climates may have drier mucous membranes than those in humid regions. So when scientists try to study the common cold, they must try to minimize these variables. That means infecting study subjects with one type of rhinovirus or coronavirus at a time and observing the progression of symptoms.
In most previous studies looking at the common cold (mainly testing various medications to relieve symptoms), researchers have measured things like subjective nasal congestion scores or the amount of air people can inhale into their nose, rather than the amount of tissues or mucus discarded. This is because collecting nasal mucus samples effectively can be very difficult: mucus is mostly water, so asking people to collect used tissues over time allows the water to evaporate, leading to unreliable results. Also, collecting tissue requires multiple trips to the lab, which is costly and time-consuming for both participants and scientists.
But some brave scientists have taken up the challenge. In a 1993 study by DAJ Tyrrell and colleagues at the UK Applied Microbiology Research Centre, 116 volunteers were infected with either a coronavirus (the kind that causes the common cold, not the kind that causes pandemics) or one of three rhinoviruses, then isolated for up to five days after infection. To test their mucus output, the scientists collected used tissues in sealed plastic bags, which they then weighed against bags of mucus-free tissues. But in the end, they didn’t report the actual volume or weight of the snot rockets. Instead, the scientists simply noted that 60 percent of people had an increase in mucus weight two days after inoculation, and up to 70 percent had a “non-zero tissue score” (i.e., they had used at least one tissue).
The real runny nose hero came from a 1990 Australian study. Carol Pinnock and colleagues at the University of Adelaide were investigating the myth that drinking milk or eating dairy products when you have a cold makes your nose runnier. The scientists gave more than 50 university students around Adelaide a rhinovirus and had them collect used tissues in plastic bags and keep food diaries. They then weighed the samples and recorded the differences between people who ate low, medium, and high amounts of dairy, providing the first concrete scientific results about how much mucus we produce.
Crucially, it’s not much. The researchers concluded that the average amount of mucus released into the tissues during a cold is a pitiful 0-30.4 grams per day. That’s about half the mass of a tennis ball! So the amount coming out of your nose isn’t a whole sink full, or even a whole coffee cup full. Dairy products also had no significant effect, even though (for unknown reasons) some students drank up to 11 glasses of milk per day.
For those of us with colds and tissues, 30.4 grams seems like a small amount. We need to study our boogers more and more. Is it our stuffy nose that makes us feel like we’re drowning in them? Or maybe some of us have really runny noses? But we can at least take some solace in knowing that this nasty jelly that’s built up in our tissues has a purpose: the mucus helps our immune system rise to the challenge and flush viruses out of our bodies along with the mucus. Our bodies protect us in the best way they can: with boogers, …
This is an opinion and analysis article and the views of the author are not necessarily those of Scientific American.
