Inhaling salt water as an aerosol spray may reduce the number of germs exhaled and therefore the spread of germs, says a small study reported November 30 by the Associated Press. The study, published in the Proceedings of the National Academy of Sciences, found that the effects lasted about six hours after using the salt-water treatment. Harvard University researchers concluded that the treatment turned nasal fluids into larger droplets that were less likely to be exhaled.
By Howard LeWine, M.D.,
Harvard Medical School
What Is The Doctor's Reaction?
Salt water may have another valuable medicinal use. Researchers from Harvard University's Division of Engineering and Applied Sciences have shown that aerosolized salt water inhalations performed every six hours dramatically reduces the amount of exhaled airborne viruses and bacteria in some people. The equipment used to inhale the sterile salt-water aerosol is similar to the nebulizer machine that people with asthma use when they visit an emergency room for an asthma attack.
The extra moisture from the inhalation treatments changes the size and weight of the droplets that contain the germs. The larger, heavier droplets are less likely to be expelled into the surrounding air, which decreases the risk of transmission to others.
These results are very preliminary; only 11 subjects were tested. Also, the salt-water treatments only work for six hours after each inhalation. Very few people will be willing to devote four 10-minute sessions each day to prevent the spread of infection when it doesn't make them feel better.
What Changes Can I Make Now?
Salt water already has several therapeutic uses. Doctors and nurses use sterile salt water, or saline, in the hospital and the office to wash out wounds and rinse a foreign body from the eye. Saline is the main ingredient of intravenous fluids. The standard solution is isotonic, meaning that the concentration of salt in water is similar to what occurs naturally in the blood.
At home, you can use salt water for gargling to help a sore throat, to rinse out the nasal passages, and to moisten the lining inside the nose when it gets too dry. There are ready-made products that you can buy to irrigate your nose, and small bottles with salt-water spray to keep it moist. Or you can make your own, which is much cheaper. To do so:
- Thoroughly clean and rinse a quart-size container that has a tight lid.
- Pour 16 ounces of distilled, filtered or previously boiled water into the container.
- Add one teaspoon of pure salt, such as kosher salt or sea salt (rather than table salt) and shake.
- Add one teaspoon of baking soda (NOT baking powder) to buffer the solution.
- Shake thoroughly.
- For comfort, bring the water to room temperature or slightly warmer before use.
- It's best to discard the unused portion after seven days.
The isotonic solution is good for gargling, nasal moisturizing spray, and washing wounds. For a very congested nose caused by allergies or infection, a more concentrated solution called hypertonic saline may be used. To make this, you would add an extra teaspoon of salt to the above mixture. The extra salt draws moisture out of a congested nose. You don't want to use this for a dry nose.
You can safely gargle with isotonic saline frequently for a sore throat. You can use a nasal saline spray as often as needed for a dry nose. Nasal irrigation requires more care. You should limit this to two to three times per day unless instructed differently by your doctor. Also you should not perform this treatment if you have acute sinusitis.
What Can I Expect Looking To The Future?
I think the researchers are on to something. This is the first leg of what will likely evolve into improved techniques that will decrease airborne transmission without using drugs. The challenge will be find a therapy that only needs to be given once or twice per day at very little expense. Then it can be compared to the simplicity of hand cleaning as an easy way to help prevent the spread of infection.
