A 55-year-old man with previously normal taste and smell treated a cold with a 2% zinc gluconate spray (Zicam). He noticed immediate burning in the nose, as well as anosmia, and did not use the spray again. Tests of smell function performed 13 and 23 months after the incident demonstrated severe hyposmia. Subsequently, a total of 10 patients from the Department of Otolaryngology, University of Colorado School of Medicine, were identified who had previously normal taste and smell, and who developed immediate, severe burning of the nose, followed by severe hyposmia with parosmia or anosmia, after the use of intranasal zinc gluconate. The severe hyposmia or anosmia appeared to be long lasting or permanent in some cases.
Comment: 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.
Although loss of smell was not reported in clinical trials of intranasal zinc, research from the 1930s suggested that zinc ions are toxic to olfactory epithelium. In 1937, during a polio epidemic in Toronto, 5,000 children received intranasal sprays of 1% zinc sulfate and 0.5% Pontocaine on 2 separate occasions, 10-12 days apart. It had been theorized that zinc ions would coagulate proteins in the olfactory epithelium, forming a protective coating around the nerves, thereby preventing them from absorbing poliovirus. The treatment did not prevent polio, and 10-13% of the children developed anosmia, apparently permanently. In 1976, mice subjected to intranasal irrigation with a 1% aqueous solution of zinc sulfate demonstrated degeneration and subsequent regeneration of the olfactory epithelium.
The fact that anosmia was not found in clinical trials suggests that this side effect 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. Zinc lozenges are also effective for adults (but apparently not children) with colds, and they do not appear to cause problems with smell function.
Jake BW, et al. Anosmia after intranasal zinc gluconate use. Am J Rhinol 2004;18:137-141.
COPYRIGHT 2005 The Townsend Letter Group
COPYRIGHT 2005 Gale Group
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