Last year, FDA cited more than 100 reports of loss of smell among people using Zicam products. As a result Zicam manufacturer Matrixx Initiatives pulled the three products – Zicam Cold Remedy Nasal Gel, Zicam Cold Remedy Swabs, and Zicam Cold Remedy Swabs for kids from the shelves. But the company denied that there is any link between their use and loss of smell. Rather they supported the fact that loss of smell resulted from colds or sinus conditions. After a year, a report analysis documented that Zinc nasal sprays can cause anosmia, a loss of sense of smell.
About the study
The research is based on the statistical method – Bradford Hill criteria that establish a cause-and-effect link between an environmental exposure and development of a disease to confirm that zinc-containing nasal products can cause loss of sense of smell.
The analysis included 25 patients treated at the University of California, San Diego Nasal Dysfunction Clinic, complaining of anosmia after they used the zinc gel nasal spray.
The criteria include strength of the association, consistency, specificity, temporality, dose-response, biological plausibility, biological coherence, experimental evidence, and analogy. The main findings include:
- Based on the Bradford Hill criteria, researchers found that intranasal zinc gluconate therapy causes both hyposmia and anosmia.
#008000;">Strength- In terms of first criteria, the researchers mentioned that all 25 patients had intense burning “between the eyes” and perceived the loss of smell within 12 to 36 hours, and zinc was the “only intervention” they used.
- Consistency– Davidson and Smith wrote that the relationship has been reported in peer-reviewed medical journals by multiple people in different geographic locations at different times.
- Plausible- The association is plausible — another important Bradford Hill characteristic — because it can destroy olfactory receptor cells, potentially through the inhibition of carnosine synthesis.
- Analogy– In terms of analogy, other airborne and topical compounds have shown to cause temporary or permanent anosmia, including ammonia, chlorine, and cadmium.
The findings were published in the July issue of the Archives of Otolaryngology.
Intranasal zinc gluconate is a popular over-the-counter alternative therapy for treatment of the common cold. FDA is required to inspect and monitor the safety of these popular remedies before it can cause damage to the users.