Saline is a mixture of salt and water used across medicine and home health care for everything from rehydrating patients in hospitals to rinsing out stuffy sinuses. The most common form, called “normal saline,” contains 0.9% sodium chloride, a concentration that closely matches the salt level in your blood and body fluids. This makes it gentle on cells and tissues, which is why it shows up in so many different medical and everyday situations.
Why 0.9% Salt Matters
Your blood plasma has a natural salt concentration that your cells are built to handle. Normal saline matches that concentration, making it “isotonic,” meaning it won’t cause cells to swell or shrink when it comes in contact with them. That’s the core reason saline is so widely used: it’s compatible with the body in a way that plain water is not. Pure water, by contrast, can damage cells because fluid rushes into them through osmosis, causing them to burst.
Treating Dehydration and Blood Loss
The single most common use of saline worldwide is replacing lost fluids. When someone is dehydrated from vomiting, diarrhea, heat illness, or blood loss, saline delivered through an IV restores fluid volume quickly. It’s a frontline treatment in emergency rooms for hemorrhage, sepsis, and shock. For infectious diarrhea with severe dehydration, guidelines recommend IV saline or similar fluids when a patient can’t keep oral fluids down.
Normal saline is also the go-to fluid for blood transfusions because it doesn’t contain calcium or sugar, both of which can interfere with transfused blood. And it’s routinely used to flush IV lines and dilute medications before they enter the bloodstream.
That said, saline isn’t always the best IV fluid. For large-volume resuscitation, especially in sepsis, balanced solutions like Lactated Ringer’s are now often preferred. Normal saline has higher chloride levels than your blood does, and infusing large amounts (more than a liter a day) can tip the body’s acid-base balance, creating a condition called hyperchloremic acidosis. This excess chloride can also reduce blood flow to the kidneys. One exception: for brain injuries, normal saline is often still preferred because its slightly higher concentration helps limit brain swelling.
Clearing Congested Sinuses
Saline nasal irrigation is one of the best-supported home remedies for sinus congestion, allergies, and chronic sinusitis. Rinsing your nasal passages with salt water thins mucus, flushes out allergens and irritants, and helps the tissue lining your sinuses heal. Ear, nose, and throat specialists routinely recommend it after sinus surgery to clear debris and prevent scar tissue from forming.
The method matters. A large-volume, low-pressure rinse (using a squeeze bottle or neti pot) works significantly better than a simple saline spray. In a randomized trial, people using irrigation had 50% lower odds of frequent nasal symptoms compared to those using a spray alone. By eight weeks, 40% of the irrigation group still reported frequent symptoms versus 61% in the spray group. So if you’re only using a quick spritz, switching to a full rinse is worth the effort.
Cleaning Wounds
Saline is the standard solution for washing out cuts, scrapes, and lacerations before they’re closed. Because it’s isotonic, it doesn’t damage exposed tissue or interfere with healing the way some antiseptics can. Studies have found that more expensive wound-cleaning options, including antiseptics like povidone-iodine and specialized detergents, offer no advantage over simple saline in preventing infection.
In clinical settings, wounds are typically irrigated with about 500 mL of saline delivered with enough pressure to dislodge debris without harming tissue. At home, gently pouring or squirting saline over a minor wound serves the same basic purpose: flushing out dirt and bacteria before you bandage it.
Helping People With Cystic Fibrosis Breathe
A stronger version of saline, called hypertonic saline (typically 3% to 7% salt), is used as an inhaled treatment for cystic fibrosis. The higher salt concentration draws water into the airways, thinning the thick, sticky mucus that characterizes the disease and making it easier to cough up. In a randomized trial of children and adults with CF, inhaling 6% saline twice daily improved lung function by 15% within two weeks, compared to just 3% in those using normal saline. A longer 48-week trial found that the hypertonic saline group maintained better lung function, had fewer flare-ups, and missed fewer days of normal activities. This stronger concentration is also being studied for other lung conditions involving excess mucus, including bronchiectasis and COPD.
Contact Lens Rinsing
If you wear contact lenses, you’ve likely seen saline solution on the shelf next to multipurpose solutions. These are not interchangeable. Saline rinses your lenses before you put them in, washing away loosened debris and residual cleaning solution. It does not disinfect. Multipurpose solutions both clean and kill germs. Using saline alone to store your contacts overnight leaves bacteria on the lens and raises your risk of eye infections.
Making Saline at Home
You can make saline for nasal rinsing or wound cleaning at home, but the water source is critical. The Cleveland Clinic recommends combining 3 teaspoons of non-iodized salt with 1 teaspoon of baking soda as a dry mix, then stirring 1 teaspoon of that mixture into 8 ounces of lukewarm water.
The water must be either distilled, labeled sterile, or tap water that has been boiled for three to five minutes and then cooled. Never use water straight from the faucet. Tap water contains low levels of bacteria that are harmless when swallowed but can cause serious infections when introduced into your nasal passages or an open wound. Any leftover boiled water should be stored in a sealed, clean container and discarded after 24 hours.
Homemade saline is only appropriate for external uses like nasal irrigation and wound rinsing. It is not sterile enough for use in the eyes or for any purpose involving injection.