On average, the typical American contracts two to three colds per year between September and May, at an estimated cost of around $40 billion to the economy. Effective forms of treating or preventing colds have proven hard to come by, with the majority of over-the-counter medicines yielding modest results; it’s hard to devise a drug that tackles the vast array of viral pathogens that cause them. The need for better respiratory protection during the winter months is clear. It might be found in a practice that dates back thousands of years.

The concept of saline nasal irrigation, or bathing the nasal passages with a saltwater solution, is thought to have been introduced as part of Ayurveda, an alternative medicine system that originated in the Indian subcontinent more than 5,000 years ago. Now, modern science is beginning to demonstrate that this ancient practice really does serve as a surprisingly effective shield against many of the seasonal bugs behind the common cold.

In 2024, a major new study of nearly 14,000 people funded by the National Institute for Health and Care Research in the UK found that using a simple saline-based nasal spray between three and six times a day at the first sign of an infection reduced illness duration by around 20 percent. A follow-up study, published last year, reported similar benefits.

According to Paul Little, a professor in primary care research at the University of Southampton who led both studies, sodium chloride—the chemical name for salt—is capable of stimulating a natural antiviral mechanism within the nose. “The chloride in saline is taken up by the cells of the nose and throat, and converted into hypochlorous acid within these cells which inhibits viral replication,” says Little. “In doing so, the viral load in the nose is reduced.”

Archived medical journals reveal that this practice has been examined as part of Western medicine since the 19th century, but has often been treated with a degree of skepticism. During the early stages of the Covid pandemic, many health care professionals dismissed the suggestion that saline nasal irrigation might be able to prevent infections. The technique was initially listed among other debunked therapies on the World Health Organization’s Covid myth buster page, before being later removed as a steady trickle of research began to prove that regular use of saline sprays or irrigation really could limit the effects.

One study found that people who practiced saline nasal irrigation for two weeks after testing positive for Covid were more than eight times less likely to be hospitalized, leading to a resurgence of interest among doctors regarding its ability to dampen the effects of other seasonal infections.

“Clinicians and researchers have started paying increasing attention to saline nasal irrigation because it helps, and it is natural, easy to understand care,” says David Rábago, a physician and professor at Pennsylvania State University College of Medicine. “So far the results of many small studies and a few big ones are that saline nasal irrigation is safe and effective.”

As well as blocking viral replication within nasal cells, it appears that saline can increase the activity of a group of white blood cells called neutrophils—which help to fight off pathogens—while also enhancing the ability of mucus to encircle and trap viruses.

“When perfectly hydrated, the mucus cells make a barrier and envelop a virus, so that you can either swallow it where the [stomach] acid degrades it, or cough it up,” says Amy Baxter, a pediatrician and assistant clinical professor in medicine at Augusta University. “It’s kind of like how soap works; it surrounds the dirt and makes it easier for it to come off because it fully envelopes these little particles.”

According to Baxter, a well-hydrated nasal tract may also make it harder for a virus to latch onto the receptors within the nose that it uses to enter the body, such as the ACE2 receptor used by some coronaviruses. “Studies have found that the stiffer and drier these ACE2 receptors are, the easier it is for a virus to get on them,” says Baxter. “The more liquid the nasal microbiome, the harder it is for the virus to catch onto them, as it’s a moving target.”

There are still various questions about nasal rinsing, ranging from the optimal salt concentration to the ideal dosage, and the best method of application. (Baxter says you can make your own solution through mixing eight ounces of water with half a teaspoon of salt and half a teaspoon of baking soda.) While saline nasal irrigation was traditionally carried out through pouring lukewarm salt water into the nose via a teapot-like vessel called a Neti pot, Little’s study achieved remarkable results with a simple pump-action saline spray that can be purchased cheaply from any pharmacy.

While the average participant in Little’s study was able to achieve significant protection through spraying their nose with saline three times a day, Baxter says that older men, particularly those who are significantly overweight, stand to benefit the most. “Older males have the biggest amount of nasal real estate which means they’re more vulnerable to a higher viral load,” she says. “Essentially, the more surface area you have, the more volume of saline you need as well.”

If you’re preparing your own saline solution, it's important to first distill or boil the water you're using, or use melted ice water. This is to avoid potentially fatal infections with a brain-eating amoeba known as Naegleria fowleri, which does affect a handful of people in the US every year, particularly in southern states.

Researchers are now keen to explore whether saline nasal irrigation can offer a means of preventing the spread of colds as well as mitigating their severity. Further studies are likely to examine the benefits of gargling saline, as many respiratory viruses also enter the body orally and access receptors in the tonsils and the back of the throat.

In the meantime, Baxter and others are now regularly applying saline sprays or irrigation as a means of protecting themselves from infections, especially during the winter months or while travelling. She says that she tries to rinse her nose with eight ounces of saltwater before going into any situation where she might be at a greater risk of picking up an infection, and if she’s been in close contact with anyone with a cold, she tries to spray or irrigate her nasal cavity as quickly as possible.

“The faster you do so after you’ve been exposed, the better,” she says.

Update 1/8/26 11:05am ET: This story has been updated with more detail on preparing your own saline solution.