Nasal Sprays: More There Than Meets the Nose?
May 14, 2001 -- A common ingredient found in nasal saline sprays be may doing more harm than good, according to new research out of Eastern Virginia Medical School in Norfolk.
Over-the-counter saline sprays are used to moisten dry nasal membranes, clear debris from the nasal passageway, and improve mucous membrane function; they're also frequently used after sinus or nasal surgery. Many commercially available saline solutions have an added preservative to keep bacteria from growing in them.
The trouble appears to be with the most common preservative, benzalkonium chloride (BKC), which researchers say kills off important cells found in the nose. These cells, called neutrophils, are present all over the surfaces of the nose and mouth, and provide a frontline defense against invading organisms. There must be enough functioning neutrophils for the body to successfully fight off infections, including sinusitis.
"I think this study is important because it is the first time we are aware of that someone has shown that there are deleterious side effects to saline nasal spray," says lead author Mark Boston, MD, who presented his findings at the Triological Society's annual meeting, held this year in Palm Desert, Calif.
"Other research has shown that steroid sprays containing the preservative [BKC] can inhibit neutrophil function, but we showed that the [BKC] destroys the cells and releases intracellular content," says Boston, a senior resident in the department of otolaryngology-head and neck surgery at Eastern Virginia Medical School.
Boston and his colleagues examined under a microscope samples of neutrophils from volunteers who had rinsed their mouths with either a nasal saline spray containing BKC or a similar saline solution without the preservative. Additionally, they exposed human neutrophils to saline spray with different concentrations of BKC and for different amounts of time. In both experiments, the researchers found that the neutrophils exposed to BKC were killed off while the ones exposed to the nasal spray without the preservative remained basically intact.
"I think it is important to realize that saline nasal spray is just saltwater. It has many benefits in terms of moisturizing the nose and clearing debris and mucus, and I encourage its use when indicated. ..." says Boston. "Because it is saltwater, however, it should be safe and does not need to have preservatives added, especially when these preservatives can make symptoms worse."
But Boston conceded that his are just preliminary.
"I think further research that evaluates the potential link between the destruction of neutrophils by [BKC] and patient symptoms needs to be evaluated," he says.
Another reason to do more studies on BKC, Boston says, is that the preservative is also used in eye-drop preparations, inhalers, steroid nasal sprays, and nasal decongestants.
James Coticchia, MD, agrees that more research is needed.