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.
James Coticchia, MD, agrees that more research is needed.
"I think the study findings are very interesting. The problem is that the majority of the study is confined to [laboratory] study analyses, which are interesting and may be of some clinical importance, but it is hard to tell that without really looking at the [human] aspect too," says Coticchia, who reviewed the study for WebMD.
"It is well known that commonly used preservatives are somewhat [poisonous to cells], and certainly this study lends credence to that," says Coticchia, a pediatric otolaryngologist and assistant professor of pediatrics and otolaryngology-head and neck surgery at Case Western Reserve University School of Medicine, in Cleveland.
"It confirms some previous observations that we have seen ... about BKC interfering with neutrophil function," Jerry Schreibstein, MD, tells WebMD. "The literature in the past is somewhat mixed. I think the interesting part is what we don't know -- what the clinical significance is."
Schreibstein is director of the sinus surgery program at Bay State Medical Center in Springfield, Mass., and an assistant clinical professor of otolaryngology-head and neck surgery at Tufts University School of Medicine in Boston. He also reviewed the study for WebMD.
"Preservatives do have the potential side effect of impairing the function of white blood cells, but the jury is still out whether these things really cause long-term damage to the nasal membranes and whether the preservative actually causes an increase in infections," says Schreibstein.
"I think there is still benefit in using saline nasal spray, and people shouldn't be alarmed by these studies, they just give us food for thought and encourage to do more research," he says.
Having said that, Schreibstein adds, "If you can avoid using any unnecessary substances, that is great. If you can find something preservative-free, that would be helpful, or make some up on your own, but you would have to make up a fresh batch every day."
Schreibstein says making a fresh batch every day or using a solution with a preservative prevents bacteria or mold from being introduced into the nasal passages.
"Whenever you release a study that contains useful information but that is not directly clinically applicable, you always risk that patients will overreact," says Coticchia. "In other words, I can't tell you from this study whether it is more beneficial to use normal saline with [BKC] vs. not using saline at all.
"If you have a choice of using normal saline without preservatives vs. using normal saline with preservatives, [the findings] lead you to believe that normal saline without preservatives would be better -- but it may not necessarily be the case," he says.
"For patients it is always a good idea to read labels and know what you are putting into your body," says Boston. "If you are using saline spray and are experiencing symptoms of nasal irritation, congestion, or drainage, you should talk to your physician."