Jan. 7, 2003 -- New research suggests that the length and severity of a cold may be cut in half when treatment with a zinc nasal spray is started within two days of the onset of symptoms.
In previous studies that showed relief from the use of such zinc sprays, significant relief was achieved only when these products were used within the first 24 hours of the first signs of sniffling, congestion, hoarseness, and sore throat, says study researcher Sherif B. Mossad, MD, FACP, FIDSA, of The Cleveland Clinic.
"No one really knows why zinc works, but there are several theories," he tells WebMD. "My feeling, and the leading theory, is that the zinc blocks the cold virus from combining with surface proteins that trigger symptoms."
In his study, published in the January issue of the medical journal QJM: An International Journal of Medicine, patients using Zicam, an over-the-counter nasal spray, cut the length of their colds an average of 1.5 days compared with those treated with a placebo. However, some patients slashed their cold duration in half -- from six days to only three.
The study was paid for by the makers of Zicam, a spray that sells for about $10 and is available at most drug stores.
This study, which involved 80 patients who were in their first two days of a new cold, is now the sixth to show that colds could be shorter and less severe when using over-the-counter products containing zinc, says Mossad, an infectious diseases specialist. But eight other published studies showed no benefit from using these products. Three of those trials showing relief involved the use of nasal sprays, and one has shown use of the spray could halve a cold's duration, but only when taken in the first day of illness.
"The spray contains the same type of zinc gluconate that is in lozenges [such as Cold Ease], but I cannot say whether there is an advantage of using a spray administered in the nose over something that is put in the mouth," he tells WebMD. "I think it's a matter of personal preference. I've tried both and think that people could probably consider one of them to shorten the length of a cold. But theoretically, a spray might be better because colds originate in the nose and eyes, so if you take action at the point of entry, I would think that might be an advantage."
His study did not compare the benefit of sprays vs. lozenges.
The finding did not surprise Sabrina Sobel, PhD, of Hofstra University, a researcher who co-authored several papers examining how zinc lozenges affect cold symptoms and duration.
"In our studies, the best benefit came when the lozenges were taken within 24 hours of the first sign of symptoms, cutting colds by almost in half," she tells WebMD. "If you take zinc lozenges within 48 hours, there was some relief, but not as dramatic -- it cut cold duration by only about one-third."
She says that zinc acts as a physical barrier that prevents viruses from gaining entry into cells that line the nose and throat, "sort of like clogging a keyhole with a lot of pieces of sand. Every zinc ion acts like a piece of sand."
In Mossad's study, half of the participants -- all between ages 18 and 55 -- used the spray four times daily in each nostril, beginning within 48 hours of the first onset of symptoms; the others received a placebo. The participants did not know which they received. Those using the spray not only got over their colds more quickly, but they showed measurable improvement in most symptoms, especially a reduction in nasal drainage and congestion, hoarseness, and sore throat.
Nasal stinging or burning was the most reported side effect. No study to date has examined how zinc products affect children, who typically have up to six colds a year -- about three times as many as adults.
"I think the message is that you need to take action fairly quickly, within the first 48 hours of the beginning of a cold, because beyond that, the benefit will be minimal," says Mossad. "However, all previous evaluations [of zinc spray] showed effectiveness of treatment that was started in the first 24 hours of symptoms. With our study, the treatment could be started as late as the second day of illness."
Use of a zinc product does not help prevent colds, he adds, and long-term ingestion of excess amounts of this trace element can weaken immunity and may decrease levels of HDL "good" cholesterol.