SALT IN A WOUND
The Myth of Preventing Infection by Rinsing with Seawater
Imagine for a moment that you’re stranded on a remote coastal shoreline. As you climb over the slick rocks, your foot slips and you fall forward, slamming your forearm against the edge of a sharp stone. Feeling dizzy and nauseated, you examine your arm and see a deep bleeding gash flecked with sand and grit from the fall.
Reeling from your injury, you recall hearing that saltwater can kill bacteria, and you know that hospitals often rinse wounds with saline solution. So, you contemplate washing out your wound with seawater with the hope of preventing infection. Unfortunately, it’s likely that doing so will make your situation even worse.
Despite pervasive claims about infection prevention, the scientific consensus is clear: rinsing your wounds with seawater is dangerous.
Like most myths, the supposed healing properties of seawater are founded on a grain of truth. Salt is certainly capable of preventing the growth of some types of bacteria. High salt concentration in liquid creates a hypertonic solution that pulls moisture out of susceptible bacteria cells via osmosis, slowing or stopping their growth.
For thousands of years, salt curing has been used to preserve meat, and salt was used as a primitive antiseptic in ancient Egypt, Greece, and Rome. You’ve probably heard the phrase “rubbing salt in a wound,” a saying that’s rumored to have originated from sailors who would rub the crystals on the cuts they received from lashings. Salt in these wounds intensified pain and caused scarring, but the men suffered through it in a desperate attempt to avoid deadly infections.
Gargling warm saltwater can be beneficial for oral health, as mentioned in our health column, Off-the-Grid Dentistry, elsewhere in this issue. Most notably, saline solution is widely used by medical professionals to irrigate wounds. However, there are two critical differences between medical saline and seawater.
Salinity: Medical saline is isotonic, and typically contains 0.9-percent salt to mimic the body’s natural salinity — that’s why there’s no excruciating burn when it’s applied. Saline irrigation is intended to flush out the wound rather than kill bacteria on a cellular level.
Seawater is hypertonic, with salinity of about 3.5 percent. This causes a painful stinging sensation as it draws water out of the exposed cells in a wound. The higher salinity is capable of killing some types of bacteria, but other salt-tolerant microorganisms thrive in seawater. This leads to our next point.
Sterility: Medical saline won’t introduce new bacteria into your wound, but seawater is far from pure. It can contain traces of human pollution, such as sewage or chemical runoff, and it’s teeming with a variety of microorganisms, including:
Dinoflagellates that cause red tide and produce harmful biotoxins
Enteric viruses that cause gastroenteritis, hepatitis, myocarditis, and aseptic meningitis
Protozoan cysts such as cryptosporidium and giardia, which are washed out from freshwater sources and can remain infectious for up to 12 weeks in seawater
Staphylococcus aureus, the bacteria that causes staph infections Vibrio bacteria, a category that causes serious diseases. This includes V. cholera, the bacteria strain responsible for the infamous disease of the same name.
In an essay published by ABC News, Wake Forest University Professor John G. Spangler, M.D. wrote, “Marine vibrios can infect the bloodstream, causing potentially fatal illness. Skin infections, which occur when open wounds are exposed to sea water, can lead to large areas of blistering as well as deep skin and muscle infections. These also are extremely dangerous and often fatal.”
Knowing the risk of infection from seawater, it’s worth considering alternate treatments that could be applied in scenarios such as our hypothetical beachcombing incident.
Sterile saline is an easy choice, but you probably won’t have any unless you’re carrying a first-aid kit. Don’t bother trying to improvise your own saline with table salt — getting the correct pH and isotonic salt concentration while maintaining sterility isn’t feasible outside a lab.
Fortunately, clinical studies have indicated that saline solution isn’t substantially more effective at preventing infection than clean tap water. In fact, a clinical study published in 2013 in the BMJ Open medical journal found that slightly fewer infections occurred when using tap water, calling it “a safe and cost-effective alternative to saline solution for wound irrigation.”
This means you can simply rinse your wound thoroughly with clean drinking water. Proper wound irrigation requires some pressure to wash away debris — this can be achieved by squirting water out of a clean syringe, squeeze bottle, or even a plastic bag with a slit in the corner. Then, apply a dressing to keep the wound clean and do your best to find some antibiotic ointment, or better yet, a hospital.
WARNING: This article is meant to be a quick overview and not a detailed guide on emergency wound care. Professional medical treatment should always be sought before attempting any of these methods.