The 5,000-year-old hack that could cut your sick days by 20% - or prevent some illnesses entirely

Nasal saline is just not cool enough.

Would I use a nasal saline spray or rinse to help treat Covid, flu, and other nasty respiratory illnesses? Absolutely. I would.

What about to help prevent those infections from taking hold in the first place? Sure. I would. I have.

I think we are leaving a cheap and easy way to help prevent/treat respiratory infections on the table. A missed opportunity to help prevent flu and Covid and RSV and the rest. It is one of the few archaic medical practices that has survived the scrutiny of evidence-based medicine. You know, nasal saline — sprays, rinses, and some techniques in between?

It’s unglamorous, unprofitable, and not so buzzworthy. Nerdy perhaps. But the use of nasal saline irrigation as a medical treatment dates back over 5,000 years to the ancient Hindu Ayurvedic tradition, where the practice called jala-neti was performed daily for personal hygiene. Ancient Greek and Roman physicians also developed nasal lavage devices, showing that multiple civilizations independently recognized the benefits of washing nasal passages with salty water. After being documented in medical journals like The Lancet in 1902, the practice surged in Western medicine, especially as those intrepid physicians had few weapons of worth against infections. Modern research validates what ancient practitioners knew - that saline irrigation effectively removes pathogens and debris while creating an inhospitable environment for viruses

As flu season, the predictable holiday Covid wave, RSV season, and the rest of the miserable, pointless viruses bear down upon us, many ask about simple interventions that might help prevent or treat illnesses. We have good hygiene, vaccines, ventilation, and sometimes antivirals. But today’s review will examine the current evidence for not overlooking or underestimating nasal saline in terms of:

• preventing respiratory illnesses

• potential as post-exposure prophylaxis

• established role in treating viral infections.

Understanding the biological rationale

The nasal cavity serves as the primary portal of entry for respiratory viruses including SARS-CoV-2 and influenza. Nasal ciliated epithelial cells are the initial targets for viral entry, and after replication, viral particles are released at the cells’ apical surface (facing into the air passages), allowing progressive infection and spread to the deeper airways. The concept of micro-aspiration—whereby virus, mucus, and inflammatory junk from the oral and nasal cavities spread to the lower respiratory tract—is increasingly recognized as a key mechanism driving progression from upper to lower respiratory tract disease.​

Based on current evidence, including recent research accelerated by the Covid pandemic, the mechanisms by which nasal saline irrigation reduces viral infections and aids treatment can be categorized into physical clearance, enhancement of innate immunity, and direct intracellular antiviral effects.

1. Physical clearance & mechanical removal

The most immediate mechanism is simply the rinsing effect, which physically reduces the burden of pathogens and inflammatory byproducts. Think itsy bitsy spider.

• Viral load reduction: Saline irrigation mechanically flushes viral particles from the nasal cavity and nasopharynx, reducing the viral load available to infect local cells or be aspirated into the lungs.​

• Removal of inflammatory junk: Irrigation helps removes local inflammatory cytokines (e.g., IL-6, IL-8), histamine, leukotrienes, and prostaglandins from the nasal mucosa. This reduction in chemical mediators helps alleviate congestion and local inflammation.​

• Bioaerosol hygroscopic growth: Any fluid engineers reading? Apparently saline alters the physics of exhaled droplets. The addition of saline causes respiratory droplets to grow via hygroscopic absorption of water. These larger droplets deposit in the upper airways (where they can be cleared) rather than remaining as fine aerosols that penetrate deep into the lungs.​

2. Enhancement of mucociliary clearance

Nasal saline can help the function of the mucociliary transport system, the upper respiratory tract’s primary defense mechanism and broom.

• Ciliary beat frequency: Saline irrigation improves the frequency of ciliary beating, which is often impaired during viral infections.​

• Mucus thinning: Viral infections often produce thick, viscous mucus that traps bacteria and viruses but is difficult to clear. HOCCKKK! Eww, sorry. Saline hydrates the mucus layer, reducing viscosity and elasticity, which facilitates more efficient transport of pathogen-laden mucus toward the nasopharynx to be swallowed and obliterated by stomach acid.​

3. Innate immune biochemistry (hypochlorous acid production)

Recent research, particularly from the ELVIS (Edinburgh and Lothians Viral Intervention Study) trials, highlights a biochemical mechanism where saline fuels the body’s own antimicrobial production. And yes, there is a bunch of Scottish nasal saline trials under the acronym ELVIS. Combining Scottish anything with Elvis something is the world’s most reliable way to make something cool.

• Generation of hypochlorous acid: Nasal epithelial cells and innate immune cells (like neutrophils) possess peroxidase enzymes. These utilize intracellular chloride ions provided by the saline solution to convert hydrogen peroxide into hypochlorous acid. Viruses hate to be doused in such acid.

• Virucidal action: Hypochlorous acid is a potent oxidizing agent (similar to the active ingredient in bleach) that has broad-spectrum antiviral activity. By increasing the availability of the chloride substrate, saline irrigation effectively supercharges this innate intracellular defense mechanism, leading to the direct inactivation of viral particles.​

4. Intracellular & molecular inhibition

Studies investigating SARS-CoV-2 specifically have identified novel molecular pathways by which saline—particularly at hypertonic concentrations—interferes with viral life cycles.

• Inhibition of furin protease: The enzyme furin is a host protease that many coronaviruses (including SARS-CoV-2) hijack to cleave their spike proteins, a necessary step for cell entry and fusion. Hypertonic saline has been shown to inhibit furin activity, effectively locking the virus out of host cells.​

• Membrane depolarization: When there’s a lot of salt outside cells, it opens special channels that change the electrical charge across the cell membrane. This puts the cell into a “low energy mode” where it has less available fuel to power its normal activities. While this doesn’t harm the cell itself, it creates conditions that make it much harder for viruses to replicate, since viral reproduction requires a lot of energy from the host cell. Essentially, the salt water creates an environment where viruses can’t as effectively hijack the cell’s machinery to make copies of themselves.

• Inhibition of viral replication: In vitro studies have observed a dose-dependent reduction in viral replication, with isotonic saline (0.9%) reducing replication by ~50% and hypertonic saline (1.5%) achieving near 100% inhibition in some models.

Clinical applications and evidence

Alright, we made it through the hard/fun scientific part. Now what about the family doctor stuff, in which we care more about patient outcomes and the zoomed out big picture?

Prevention of infection and post-exposure prophylaxis

Nasal saline can reduce your chance of getting sick, but it is hard to pin down by just how much.

The Immune Defence trial, a large multicenter randomized controlled trial conducted in UK primary care and published in The Lancet, enrolled 14,000 adults at increased risk for respiratory illness. People were randomized to isotonic saline nasal spray, a gel-based spray, a behavioral intervention, or usual care. Over six months, the saline spray group experienced a 20% reduction in total illness days compared to usual care, with sustained benefit over 12 months (mean 18 vs. 22 days). The instructions were to use two sprays per nostril at the first sign of an infection or after potential exposure to infection, up to 6 times per day. So people weren’t using the sprays routinely every day - they only started using them when they felt symptoms beginning or after they thought they’d been exposed to someone who was sick. This makes the results particularly interesting, since the sprays were only used reactively when illness was starting, yet still reduced total sick days by about 20% over the 6-month study period.

In a randomized controlled trial published in Scientific Reports, hypertonic saline nasal irrigation and gargling reduced common cold household transmission by 35% and decreased viral shedding.

Systematic reviews and expert consensus statements corroborate these findings, noting that daily saline nasal hygiene modestly reduces household transmission. For Covid, a systematic review found that nine out of ten studies on saline-based solutions reported positive effects in reducing nasopharyngeal viral load, with four studies demonstrating a reduction in transmission with saline irrigation.

Let’s say you go to a wedding, or a Slayer concert with a mosh pit, and you want to reduce your risk of getting sick from said joyous event. If you go home and use some nasal saline, flush and gently blow out the lines, will that reduce your risk? I think so. Viral doses absolutely matter. Like my epidemiology and old school blogging friend Dr. Tara C. Smith once wrote:

So while we are constantly inundated by microbes, the number of microbes that enter our bodies is usually too low to get past our defenses. (A tiny enough dose may even serve to remind our immune system of a pathogen’s existence, boosting our antibody response to keep us protected against it.)

When enough pathogens do manage to breach our defenses and start to replicate, we get sick. Often this is just a numbers game. The more invaders you’re fighting off, the more likely you are to feel ill.

Treatment of illness and symptom relief

Nasal saline sprays and rinses are supported by moderate-quality evidence for modest reductions in symptom severity, duration, and healthcare utilization in the treatment of established viral URIs, including Covid and influenza. Not game changers, but game strategy improvers.

That pilot randomized controlled trial mentioned above evaluated hypertonic saline nasal irrigation and gargling in healthy adults within 48 hours of URI onset. The intervention group demonstrated a reduction in illness duration by ~2 days, decreased use of over-the-counter medications, and a 35% reduction in household transmission.

A randomized controlled trial recently presented at the European Respiratory Society Congress found that saline nasal drops can reduce the duration of the common cold in children by 2 days compared to usual care. The study, which included 407 children up to 6 years old, showed that those using saline drops experienced cold symptoms for an average of 6 days, compared to 8 days for those receiving usual care. Additionally, the use of saline drops was associated with a lower rate of household transmission, with fewer family members catching colds in households where children used the drops.

A systematic review by the Cochrane Database assessed saline nasal irrigation for acute URIs, including the common cold and sinusitis. The review found that saline irrigation has benefits for relieving symptoms, particularly nasal congestion and obstruction, with one larger pediatric trial showing statistically significant reductions in nasal secretion and obstruction scores. However, the Cochrane folks pointed out that the clinical significance of these reductions was modest, and the overall quality of evidence was low due to small sample sizes and risk of bias.

For Covid, multiple studies and systematic reviews have reported that saline nasal irrigation reduces nasopharyngeal viral loads, hastens viral clearance, and provides significant symptom relief, particularly when initiated early in the course of illness.[1][2][3][4][5] For one example, a case-control study found that daily isotonic saline lavages significantly decreased nasal symptoms (blocked nose, runny nose, sneezing) by an average of 25%, with high patient satisfaction and only rare, mild adverse effects.

Another small study early in the pandemic looked at 80 high risk patients who were started on nasal saline irrigation twice daily for 14 days starting within 24 hours of their positive Covid test. This was not a randomized trial, but an 8-fold reduction in hospitalization rates was observed when compared to the matched control general population. But this study design was only good enough to make this worth further confirmatory research. I’m still waiting.

Here are the results of another study on symptom reduction (I made this table) for patients with Covid:

Risks of nasal saline

Nasal saline sprays and rinses are generally very safe for the general population in both outpatient and inpatient settings, with only minor and infrequent risks. The most common adverse effects are local and transient, including nasal burning, irritation, discomfort, and fluid dripping from the nose. If saline starts coming out of your ears you have done something quite wrong. Side effects are more frequently reported with hypertonic saline formulations compared to isotonic saline, and with high-volume irrigations compared to sprays.

A critical theoretical and known risk is infection from contaminated water used to prepare saline solutions. There have been rare but serious cases of fatal primary amebic meningoencephalitis due to Naegleria fowleri bacteria when tap water was used for nasal irrigation. To mitigate this risk, guidelines from the CDC, FDA, and specialty societies recommend using only distilled, sterile, or previously boiled water for preparing saline solutions, and regular cleaning of irrigation devices.

Commercially prepared saline sprays or rinses have a good safety record as far as I could find.

Current evidence does not demonstrate significant or lasting disruption of the nasal microbiome in the general population when using saline sprays or rinses.

These findings are consistent across multiple guidelines and systematic reviews, supporting the excellent safety profile of nasal saline sprays and rinses when used appropriately: [1][2][3][4][5][6][7][8][9][10]

Practical considerations

Based on the evidence reviewed, the following practical guidance:

Concentration: Both isotonic (0.9%, normal saline) and hypertonic (1.5–3%) solutions appear effective. Hypertonic solutions may provide modestly greater symptom relief but can cause temporary burning or discomfort; reducing salinity or adjusting technique often reduces these effects.​

Frequency: Benefits appear dose-dependent. Studies showing the strongest effects typically use irrigation two to four times daily, with some Covid protocols using irrigation every 3–4 hours during acute illness.​

Technique: Large-volume irrigation (≥60 mL) using squeeze bottles, neti pots, or pressurized devices appears more effective than low-volume sprays for established infections, though nasal sprays may be adequate especially for prevention. Combining nasal irrigation with gargling may optimize coverage of the oropharynx.​

The safest way to give this a try might be to pick up a continuous nasal mist spray like this one for $10 at CVS. The spray keeps going as long as the trigger is pressed, and a gentle nose blow after misting it all up in there clears the pipes. NeilMed also makes a bunch of products, and the University of Washington provides this how-to guide. Neti pots are tricky, but many use them. I tried once and didn’t like it.

I don’t do this stuff regularly… but when I do I use my own questionable technique. It involves reverse osmosis water that is first boiled and then cooled, a cheap nasal saline salt packet to dissolve, a 3 cc syringe with no needle, and my head tilted back. Saline in, then back out the same way. I figured a way to keep most of it from going down my throat which is impossible to describe! Sorry.

Timing: Early initiation (within 48 hours of symptom onset) appears important for maximizing benefit. Later initiation (5+ days) reduces efficacy, though some benefit has still been observed.​

Limitations of current evidence

Before I start a nasal saline medical influencer side hustle, we should be honest here. Despite encouraging findings, important limitations must be acknowledged. Most studies are small, and many were not designed to detect differences in severe outcomes like hospitalization or mortality. Study heterogeneity, including variations in saline concentration, irrigation volume, frequency, timing, and patient populations, limits direct comparisons. Some studies lack adequate blinding, and placebo-controlled trials are inherently challenging given that even water-based nasal irrigation provides some mechanical benefit.​

The Covid literature evolved rapidly during the pandemic, and many studies were conducted during different variant waves with varying baseline severity, vaccination status, and treatment standards. Post-exposure prophylaxis data remain particularly sparse, relying largely on observational evidence and intuition.

And yet this celebrity was caught using nasal saline by the paparazzi. Influential.

Conclusion

Would I use a nasal saline spray or rinse to help treat Covid, flu, and other nasty respiratory illnesses? Absolutely. I would.

What about to help prevent those infections from taking hold in the first place? Like after an event in which somebody with flu/Covid was almost certainly present. Sure. I would. I have.

I think we are leaving a cheap and easy way to help prevent/treat respiratory infections on the table. A missed opportunity to help prevent flu and Covid and RSV and the rest. Another thin layer of protection in the Swiss cheese model of preventing infections, with other slices like masking, ventilation, and vaccination having holes, too. Together they make a block of cheese. I don’t really like Swiss cheese, but I’ll eat it.

In terms of treatment I did nasal saline with my most recent URI and honestly crushed it. N=1. Science settled! Are you not entertained?!

If this post has not been deep enough, or if I’ve piqued your interest for more, here is another deep dive I wrote about other nasal sprays and Covid prevention, as well as a dive on using neomycin ointment for Covid prevention.

Cheers to your health, and may the saline force be with you this respiratory season.