Chronic sinusitis mucus is more than a symptom
Chronic rhinosinusitis is often discussed as a blocked nose, pressure, drainage, reduced smell, or recurring flares. Mucus can look like a by-product of the problem. Research over the past two decades shows that in some patients it also contains active inflammatory material. That matters because the material caught in mucus may help clinicians understand which kind of inflammation is present and how persistent the disease is.
The important correction is that mucus is not the whole explanation. Chronic rhinosinusitis is a group of conditions with different patterns. Nasal polyps, allergy, asthma, altered immune responses, microbes, anatomy, and environmental exposures can all matter. The studies below support a link between mucus and inflammation in selected groups. They do not prove that mucus alone causes chronic sinusitis, and they do not show that every person with a stuffy nose has the same disease.
The Mayo finding was real but it did not settle the cause
The article began with a 2005 Mayo Clinic study. Researchers examined tissue with attached mucus from 22 people undergoing surgery for chronic rhinosinusitis. They looked for eosinophil major basic protein, or MBP. Eosinophils are immune cells. When activated, they can release proteins that can injure airway lining cells.
The original study found intact eosinophils in tissue, while diffuse extracellular MBP was far more evident in mucus. In the laboratory analysis, mucus had a greater stained area than tissue, and mucus extracts reached concentrations the authors considered capable of harming the sinonasal epithelium. Healthy control mucus did not contain detectable MBP in that comparison.
That is a useful observation about where an eosinophil protein was found in these surgical samples. It is not a trial that removed mucus and showed that disease disappeared. It also cannot prove whether the mucus deposits started the illness, resulted from existing inflammation, or both. The older headline went further than the study could support when it said chronic sinusitis was not a tissue issue.
Newer work supports a mucus and inflammation connection
A 2024 study examined surgically collected nasal mucus from people with eosinophilic chronic rhinosinusitis and from people with noneosinophilic disease. The researchers measured viscosity, water content, computed-tomography density, wettability, dry weight, and proteins in the mucus. Mucus from the eosinophilic group was denser, more viscous, drier, and more hydrophobic. Levels of eosinophil-specific proteins correlated with those physical properties.
The 2024 mucus-properties study
That study also modeled aggregates of human eosinophils and neutrophils in the laboratory. Those aggregates had properties resembling the patient mucus. This connects inflammatory cells with the thick, sticky material that can obstruct sinuses. It does not establish that the same process drives every chronic-rhinosinusitis subtype, and the laboratory treatment experiment is not evidence for a home treatment.
Another 2024 prospective study followed 61 people with chronic rhinosinusitis and nasal polyps for 24 months after sinus surgery. The team collected mucus and blood at nine time points and compared biomarkers with the nasal-polyp score over time. Mucus periostin had a strong positive correlation with the score, reported as r = 0.89. Mucus IgE and cystatin SN also correlated with the score, though less strongly. The researchers identified mucus periostin, mucus IgE, and mucus cystatin SN as promising ways to track disease severity or early recurrence.
The 24 month mucus biomarker study
The 24 month study is especially relevant because it followed people over time rather than taking one surgical sample. A correlation still does not prove a marker caused a polyp to grow. It does show that the mucus carried information that moved with a visible measure of disease in this particular polyp group.
A separate 2024 case-control study included 81 people with diffuse chronic rhinosinusitis and nasal polyps who had already undergone at least one surgery and were using intranasal steroids. It compared 39 people with uncontrolled disease with 42 people whose disease was controlled. Interleukin-5 and calprotectin were higher in nasal secretions and polyp tissue in the uncontrolled group. In the adjusted analysis, interleukin-5 measured in nasal secretions or polyp tissue was related to the risk of uncontrolled disease.
The 2024 nasal secretion and disease-control study
This 2024 study supports the idea that nasal secretions can reflect active disease. It also gives an important limit to the old article: the study found relevant signals in tissue as well as secretions. Mucus and tissue are connected parts of the same inflamed airway. Setting one against the other is less accurate than asking which markers help describe a person's disease.
Two more studies connect mucus with symptoms
A multicenter prospective study included 258 people with recurrent nasal polyps after surgery. Researchers measured proteins in nasal secretions and compared them with reported symptoms. Higher eosinophil-derived neurotoxin in the secretions was associated with more congestion and runny nose; major basic protein was associated with sneezing. This gives the mucus findings a patient-facing connection, although the selected group had severe recurrent disease and the associations cannot establish cause.
The prospective secretion-and-symptom study
Smell is another important outcome. In a separate prospective cohort of 62 adults with chronic rhinosinusitis, researchers sampled mucus from the olfactory cleft, the part of the nasal cavity involved in smelling. Ten of 26 measured proteins correlated with smell-test scores and/or visible blockage of that cleft on imaging. The pattern differed between people with and without polyps. A mucus test is not yet a practical home or routine diagnostic test, but the result shows why a blocked sense of smell may involve local inflammation as well as physical blockage.
The olfactory-cleft mucus and smell study
What a correlation can and cannot tell us
A correlation means two measurements tended to move together in the studied group. Thick mucus and eosinophil proteins may rise together because eosinophils help change mucus. A high mucus periostin result may travel with a higher polyp score. Neither relationship alone proves the direction of cause and effect. Symptoms, prior operations, steroid use, asthma, and the type of chronic rhinosinusitis can influence these results.
The newer studies are also concentrated in people with eosinophilic disease or nasal polyps, many of whom were having surgery or had recurrent disease. Their results should not be applied automatically to every person with facial pressure, a cold, seasonal allergies, or a short-lived sinus infection. The word chronic usually refers to symptoms lasting at least 12 weeks with objective evidence of sinus inflammation, not simply any ongoing mucus.
Why this matters for a person with ongoing symptoms
The practical value of this research is better understanding, not a do-it-yourself diagnosis. Mucus can be a useful sample because it captures local inflammatory signals that may be hard to see in a blood test. That may eventually help match some patients to treatment or identify recurrence earlier. These are still research and specialist-care questions; a person cannot tell their own inflammatory subtype by color or thickness of drainage.
For persistent blockage, discharge, loss of smell, repeated flares, or facial symptoms lasting for months, a clinician can help distinguish chronic rhinosinusitis from allergy, migraine, dental causes, a structural problem, or another condition. Seek prompt assessment for swelling around the eye, vision changes, severe headache, confusion, a stiff neck, or a high fever with rapidly worsening symptoms.
How is chronic sinusitis treated?
First, confirm what is being treated. Symptoms that persist for at least 12 weeks can suggest chronic rhinosinusitis, but a clinician should also document inflammation by examination, nasal endoscopy, or CT. The presence of nasal polyps matters because it changes the range of treatment options. A constantly blocked nose may instead reflect allergy, a dental problem, migraine, or another condition. The 2025 otolaryngology guideline makes objective confirmation and checking for polyps central steps.
The 2025 adult sinusitis guideline
Saline rinsing is a reasonable first step for symptom relief. A randomized trial assigned 76 adults with a history of sinusitis to usual care or daily hypertonic saline irrigation for six months. The irrigation group reported better sinus-related quality of life, fewer symptoms, and less medication use. The trial mixed people with recurrent or chronic sinus problems, so it does not tell us that rinsing cures a confirmed subtype. Its value is more modest and practical: saline can clear accumulated secretions and help people feel better while the underlying inflammation is assessed and treated.
The randomized saline-irrigation trial
Water safety is part of the treatment. Use only distilled or sterile water, or tap water that has been boiled and cooled, and clean and dry the rinse device as instructed. Ordinary unboiled tap water can contain organisms that are safe to swallow but unsafe to introduce into the nose. A prepared saline packet avoids guessing at salt concentration. Stop or ask for advice if rinsing causes marked pain, repeated bleeding, or ear problems.
CDC instructions for safe sinus rinsing
Reducing inflammation matters too. The 2025 guideline recommends an intranasal corticosteroid, saline irrigation, or both for symptom relief. A randomized trial in 323 adults with chronic rhinosinusitis and nasal polyps found that a fluticasone delivery device improved congestion, polyp grade, and quality-of-life scores more than placebo over the blinded study period. The specific device and polyp population matter: the trial does not mean every steroid product works equally well for everyone. A clinician or pharmacist can show correct spray technique, since misdirected spray can irritate the septum and cause nosebleeds.
The randomized fluticasone trial
What about adding xylitol to a rinse? A small randomized trial of 30 people, 25 of whom completed it, reported greater improvement in symptom scores after 30 days with xylitol irrigation than with saline. That is interesting but too small to make xylitol the standard starting point. A later postoperative trial studied 70 people and reported improvements with xylitol, but its surgical setting limits what it tells us about untreated chronic disease. Anyone considering an additive should discuss it with a clinician and use a properly prepared product and safe water; the established starting option remains saline.
The small xylitol-versus-saline trial
For severe disease with nasal polyps that persists despite treatment, an ear, nose, and throat specialist can discuss further options. In two large randomized trials, dupilumab added to background nasal steroid treatment improved nasal-polyp and congestion scores more than placebo at 24 weeks. This is a prescription biologic for a selected group, not a general remedy for any sinus symptom. Surgery may also be discussed when symptoms remain burdensome or anatomy prevents adequate drainage or medicine delivery. The decision depends on examination, previous treatment, expected benefit, and the chance of recurrence.
The two phase 3 dupilumab trials
Antibiotics are not a default solution for months of congestion. The 2025 guideline advises against routine antimicrobial treatment for chronic rhinosinusitis without an acute flare. A clinician may treat a suspected acute bacterial episode separately. The original mucus study likewise does not justify antifungal treatment; finding inflammatory proteins in mucus does not prove a fungal infection. Seek urgent care for eye swelling, vision changes, confusion, severe headache, or rapidly worsening illness.
The 2025 guideline on antibiotics and antifungals
The careful conclusion
The Mayo finding remains valuable: inflammatory proteins can collect in sinus mucus, and newer studies link mucus markers with mucus thickness, polyps, poor disease control, symptoms, and smell in selected patients. These are associations, not proof that mucus alone causes the disease. Treatment should address both the secretions and the inflamed lining. For many people, that starts with a confirmed diagnosis, safe saline rinsing, and an intranasal steroid when appropriate. People with persistent symptoms or polyps may need specialist evaluation and more targeted treatment. The evidence gives readers useful actions without turning a laboratory finding into a promise of cure.
