Sea Water vs. Saline: Why Not All Salty Water Is Created Equal

/ American Physiological Society
Walking on the beach.

Credit: iStock

Sunshine, warmer temperatures and no school—summer is well underway. Summer brings with it an abundance of outdoor activities—hiking, biking and trips to the beach—plus cuts, scrapes, bumps and bruises. You might think a jump in the ocean to soak those scrapes in the salt water might help. But this isn’t always the best way to treat your injuries.

It has long been known that salt water (saline) has many medicinal purposes. Doctors and other medical professionals use it to:

  • rinse wounds before applying bandages,
  • rehydrate people with water and electrolytes through an IV, and
  • deliver lifesaving medications at a controlled rate.

However, a bag of medical saline at the local health care facility and the salt water found in the ocean are not the same. Medical saline is made of sodium chloride (table salt) and purified water. Sea water is composed of sea salt—mostly sodium chloride—and water. However, there are some major differences. First, medical saline only contains about 0.03 ounces per quart of sodium chloride. Sea water has a lot more sodium—around 1.23 ounces per quart. This salty difference means that sea water may cause you to become dehydrated (and sick to your stomach) if you drink it. But the large amount of salt would not necessarily be bad for a scrape or cut. So, why isn’t soaking cuts and scrapes in sea water a good idea?

The answer lies in the second major difference between medical saline and sea water: the purity of the water. Medical saline is sterilized, a process that kills bacteria, viruses and other harmful organisms. And in most cases, even plain water from the faucet is purified enough to rinse dirt, sand and other debris from a minor cut. On the other hand, the ocean is home to many organisms, including bacteria, microalgae, fungi and viruses. When microorganisms enter an open wound they can cause inflammation and infection, which slows healing.

So go out and enjoy the beach—but when it comes to treating your scrapes, head indoors.

Jessica TaylorJessica C. Taylor, PhD, is a cardiovascular physiologist who manages projects for a contract biomedical research organization. She loves the beach and is grateful that her work takes her to the Caribbean regularly to enjoy the sand, sun and salty water.

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