"Salina" sculpture, perhaps attributed to ancient Roman sculptor Brutus Maximus Salinas Pi.
A longer, well-referenced version of this post with graphs and illustrations was posted yesterday on my site Examined. Here is the 1000 word version! I hope it helps you :)
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Nasal saline irrigation might be one of medicine's most underappreciated interventions. It's cheap, unglamorous, and won't generate pharmaceutical profits—but the evidence suggests it deserves a place in our respiratory illness toolkit alongside vaccines, hygiene, and antivirals.
This ancient practice, dating back over 5,000 years to Hindu Ayurvedic tradition, has survived into modern evidence-based medicine for good reason. Multiple civilizations independently discovered that washing nasal passages with salt water provides real benefits. The Romans and Greeks used it, as we can see from the above sculpture (ha!). Now, accelerated by pandemic research, we better understand why it works and how to use it effectively.
How It Actually Works
The nose is ground zero for respiratory viruses. When SARS-CoV-2, influenza, or other pathogens enter, they target nasal epithelial cells, replicate, and then spread deeper into airways through micro-aspiration. Saline irrigation disrupts this process through several mechanisms:
Physical clearance is the most obvious—salt water literally rinses viral particles out of your nasal cavity, reducing the pathogen load available to infect cells or migrate to your lungs. It also removes inflammatory byproducts that cause congestion and discomfort.
Enhanced mucociliary function keeps your natural defenses working. Viral infections produce thick mucus and impair the beating of tiny cilia that sweep debris away. Saline thins this mucus and improves ciliary beating frequency, helping your body's own cleaning system work better.
Biochemical antimicrobial production is where things get interesting. Nasal cells contain peroxidase enzymes that use chloride ions from saline to produce hypochlorous acid—essentially a bleach-like substance that directly inactivates viruses. By providing chloride substrate, saline supercharges this innate defense mechanism.
Direct antiviral effects occur at the molecular level, particularly with hypertonic (extra-salty) solutions. Research shows saline inhibits furin, an enzyme viruses hijack to enter cells. It also depolarizes cell membranes, creating a low-energy state that makes viral replication much harder without harming the cell itself.
The Prevention Evidence
Can regularly using nasal saline keep you from getting sick? The data suggests yes, modestly but meaningfully.
The Immune Defence trial, published in The Lancet, followed 14,000 adults over six months. Those using isotonic saline spray at the first sign of symptoms or after potential exposure experienced 20% fewer total illness days compared to usual care—about 18 versus 22 days over the study period. Notably, participants only used sprays reactively when they felt symptoms starting, not as daily prevention.
Another study found that hypertonic saline irrigation and gargling reduced common cold household transmission by 35% and decreased viral shedding. For COVID-19 specifically, a systematic review found nine out of ten studies reported positive effects in reducing nasopharyngeal viral load, with four demonstrating reduced transmission.
The mechanistic logic is compelling: viral dose matters. If you attend a crowded indoor event and flush your nasal passages afterward, you're physically removing pathogens before they establish infection. It's not foolproof, but it's a sensible additional layer of protection.
Treatment Benefits
For established infections, the evidence shows modest but real benefits. Saline won't cure you, but it can shorten illness duration and reduce symptom severity.
A randomized trial found that hypertonic saline irrigation started within 48 hours of cold symptoms reduced illness duration by approximately two days and decreased over-the-counter medication use. Recent research in 407 children showed saline nasal drops reduced cold duration from eight to six days and lowered household transmission rates.
For COVID-19, multiple studies show saline irrigation reduces nasopharyngeal viral loads, hastens viral clearance, and provides symptom relief—particularly when started early. One study found daily isotonic saline decreased nasal symptoms by an average of 25% with high patient satisfaction.
A Cochrane systematic review confirmed benefits for nasal congestion and obstruction, though noted the clinical significance was modest and evidence quality was limited by small sample sizes.
Safety Considerations
Nasal saline is remarkably safe. The most common side effects are minor and temporary: nasal burning, irritation, or discomfort. Hypertonic solutions cause these more often than isotonic ones, and high-volume irrigation more than sprays.
The critical safety concern is water contamination. Rare but serious cases of fatal brain infection from Naegleria fowleri have occurred when tap water was used for irrigation. The solution is simple: only use distilled, sterile, or previously boiled water. Commercially prepared saline products have excellent safety records.
Current evidence shows no significant disruption of the nasal microbiome with appropriate use.
Practical Recommendations
Concentration: Both isotonic (0.9%) and hypertonic (1.5-3%) solutions work. Hypertonic may provide slightly better symptom relief but can cause temporary burning.
Frequency: Studies showing strongest effects typically use irrigation two to four times daily, with some COVID protocols using it every 3-4 hours during acute illness.
Technique: Large-volume irrigation (≥60 mL) using squeeze bottles or neti pots appears more effective than low-volume sprays for established infections, though sprays may be adequate for prevention.
Timing: Early initiation within 48 hours of symptom onset appears important for maximizing benefit.
For beginners, a continuous nasal mist spray is the easiest approach—spray generously, then gently blow your nose. Companies like NeilMed make various products with good instructions.
The Honest Limitations
Most studies are small and weren't designed to detect differences in severe outcomes like hospitalization. Study designs vary widely in saline concentration, volume, frequency, and timing, limiting direct comparisons. Adequate blinding is challenging since even plain water provides some mechanical benefit.
The post-exposure prophylaxis data remains particularly sparse, relying largely on observational evidence and biological plausibility rather than definitive randomized trials.
The Bottom Line
Would I use nasal saline to help treat or prevent respiratory infections? Absolutely. It's another layer in the Swiss cheese model of infection prevention—imperfect like masking, ventilation, and vaccination, but useful when combined with other measures.
The science is solid, the safety profile is excellent, and the cost is minimal. Are we leaving a simple, effective intervention on the table during every respiratory season? Do you ever do this? Nasal saline won't replace vaccines or replace good hygiene, but as an additional tool, it deserves consideration alongside our other prevention and treatment strategies.
Sometimes the unglamorous, ancient remedies turn out to have been right all along. Other times not so much!
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Thanks for reading and tell me what you think. Have you tried this?
Also, I’ll be dropping some important new Covid science and prevention updates later this week, so add your email to the distribution list if you want to know what’s up in Covidlandia right now.
