Zinc Nasal Spray and Sense of Smell
Zinc nasal sprays, a popular remedy for the common cold, carry a small risk of damaging a person’s sense of smell and those affected may have long-lasting or even permanent damage, reports the American Journal of Rhinology (2004;18:137–41). Nasal sprays, nasal gels, and oral lozenges that contain zinc are among the most widely used treatments for the common cold. Studies have shown that zinc ions, which are released in high concentrations from these products, can kill the virus that causes colds (rhinovirus). Zinc ions also protect the cells of the respiratory tract from damage caused by viral toxins, and may prevent rhinovirus from entering and infecting the cells of the nose. Clinical trials of zinc lozenges and nasal preparations have produced conflicting results, but a substantial number of studies have found that these treatments reduce the duration of colds by 50% or more.
Side effects reported in the clinical trials were relatively minor. Zinc lozenges caused bad taste in the mouth, irritation of the mucous membranes, nausea, or diarrhea in some cases. Users of zinc nasal preparations often experienced a slight burning sensation in the nose, but the frequency of this side effect was not significantly greater than in people given a placebo. Although loss of smell was not reported in the clinical trials, there is now evidence that nasal application of zinc can cause this side effect in a small percentage of people.
According to the new report, a 55-year-old man with previously normal taste and smell treated a cold with a nasal spray containing 2% zinc gluconate. He noticed immediate burning in the nose, as well as loss of smell, and did not use the spray again. Tests performed by a doctor approximately one and two years after the incident demonstrated that his sense of smell was still severely impaired. Subsequently, a total of ten patients were identified from the Department of Otolaryngology, University of Colorado School of Medicine, who had experienced a similar adverse reaction after using intranasal zinc gluconate.
That intranasal zinc could damage a person’s sense of smell was first recognized in the 1930s. During a polio epidemic, 5,000 children were given intranasal sprays of a zinc solution. The rationale for that treatment was that zinc ions would coagulate the proteins lining the nasal passages, thereby preventing poliovirus from entering the body. The treatment turned out to ineffective for preventing polio, and at least one in ten children whose noses were sprayed with zinc lost their ability to smell, apparently permanently. Subsequent studies in mice showed that intranasal application of zinc can damage the cells responsible for smell. The fact that this side effect was not identified in clinical trials suggests that it does not occur frequently. Nevertheless, because permanent loss of smell is a serious problem, using intranasal zinc to treat the common cold may not be worth the risk. Other natural treatments that appear to reduce the duration of colds include vitamin C, echinacea, and zinc lozenges.
Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Three Rivers Press, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Three Rivers Press, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.
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