Ancient Humors to Modern Medicine
In Ancient Greek medicine, mucus—then called phlegm—was one of the four humors balancing temperament and health. Hippocrates believed its excess in cold, wet seasons could provoke disorders like epilepsy. Today, we know mucus doesn’t shape personality—but science reveals its real purpose: to shield and signal what’s happening inside our bodies.
Guardians of the Airways
Mucus lines the nasal passages, moisturizing them and entrapping bacteria, viruses, pollen, dust, and pollution. Alongside cilia, it forms a defense barrier. Adults produce around 100 ml daily, but children are usually “snottier” as their immune systems adapt to new exposures, explains Daniela Ferreira, a respiratory expert at the University of Oxford.
The color and texture of mucus can already help indicate health status—think of it as a visual diagnostic tool. See why clear runny mucus suggests irritation, while white mucus points to viral infection, and yellow-green clots signal immune cell activity battling pathogens. Reddish tints often mean minor nose tissue damage from over-blowing.
Microbial Ecosystem: The Snot Microbiome
Just as the gut microbiome influences health, the nasal microbiome—a collection of bacteria, fungi, and viruses—plays a crucial role in immunity. It varies based on age, sex, diet, location, and even vaping habits.
A 2024 study found that survival of Staphylococcus in the nose hinges on how nasal microbes manage iron—a key discovery in infection prevention.
Ferreira is exploring probiotic nasal sprays that introduce “beneficial” bacteria to outcompete harmful microbes. Such sprays could enhance overall respiratory health and even improve vaccine response—some COVID‑19 vaccines, she notes, shaped nasal microbial balance, which in turn influenced immunity.
“We could actually develop better vaccines so people don’t even get sick — it’s all in that mucus immunity.”
Snot Transplants: A New Frontier
In Sweden, a small trial had participants squirt healthy donors’ mucus into chronically stuffy noses for five days. Among 22 adults, symptoms like cough and facial pain fell nearly 40% over three months in 16 participants. Anders Martensson of Helsingborg Hospital noted no adverse effects.
Inspired by fecal microbiota transplants this snot-based approach is still in early phases—but larger, more precise studies are already underway.
The Future of Personalized Nasal Care
As research progresses, mucus sampling during standard checkups could assess not only infections and immune readiness, but broader conditions like long‑COVID or chronic lung disease. Ferreira and her team aim to define what a “healthy” mucus ecosystem looks like, enabling targeted nasal therapies.
“Snot is the future of personalised medicine,” declares Jennifer Mulligan, a prominent immunologist.
