July 20, 2010 — Just over a year ago, the FDA warned that zinc-containing intranasal cold remedies might cause loss of sense of smell.
Now a researcher who has long argued that the sprays were harmful says he has scientific evidence to back up the claim.
Last summer, the FDA warned consumers to stop using three zinc-containing Zicam products: Zicam Cold Remedy Nasal Gel, Zicam Cold Remedy Swabs, and Zicam Cold Remedy Swabs for kids. The federal regulators cited 130 reports of loss of sense of smell among users of the products.
Zicam manufacturer Matrixx Initiatives pulled the three products from the shelves, but the company maintains that there is no link between their use and loss of smell.
In the newly reported analysis, researchers applied a statistical method used to establish a cause-and-effect link between an environmental exposure and development of a disease in an effort to confirm that zinc-containing nasal products can cause loss of sense of smell, known medically as anosmia.
University of California, San Diego professor Terence M. Davidson, MD, says the analysis supports the hypothesis.
He adds that the effectiveness of zinc-containing products for preventing or shortening the duration of colds has never been proven.
“Given that they do absolutely no good for colds and given that there is potential for harm, I see no point in putting any zinc gluconate products in the nose,” Davidson tells WebMD.
Zinc Sprays and Smell Loss
The analysis included 25 patients treated at the University of California, San Diego Nasal Dysfunction Clinic, which Davidson directs, who experienced loss of smell after using zinc nasal sprays or swabs to prevent or treat colds.
Along with colleague Wendy M. Smith, MD, Davidson applied the nine-point Bradford Hill causation environmental exposure statistical measure to assess the probability that the cold-remedy use caused the loss of sense of smell.
In lawsuits brought by Zicam users, Matrixx has maintained that loss of smell resulted from colds or sinus conditions and not use of the zinc-based nasal products.
Upper respiratory infections and nasal and sinus disease are major causes of both temporary and permanent loss of smell and diminished sense of smell.
Davidson says many of his patients and others with suspected zinc-induced smell loss reported intensely painful burning in the nose when they used the products. This was followed by loss of smell within several hours.
“This is a pain that brings people to their knees,” he says. “And soon after they get over the pain, they realize they can’t smell their coffee. This is very different from viral-induced anosmia.”
Courts Find Evidence Lacking
In an interview with WebMD, Matrixx CEO Bill Hemelt said there is no proven correlation between stinging and burning in people who used zinc nasal products and loss of sense of smell.
He notes that Matrixx’s own studies showed both zinc nasal spray and placebo sprays containing no zinc can cause occasional burning.
In 2006, Matrixx settled a lawsuit brought by 340 zinc-containing Zicam users for $12 million, and Hemelt says the company has settled other cases over the years.
But he adds that 10 judges in 10 cases have found little scientific evidence to support the claim that zinc-containing Zicam nasal products caused loss of smell.
In one such case, Davidson was rejected as an expert witness when the judge ruled his opinions on specific causation to be “seriously flawed.”
More than a dozen Zicam products remain on the market, including several oral zinc-based lozenges.
But none of the company’s nasal products still contain zinc gluconate.
“The products at issue were removed voluntarily more than a year ago,” Hemelt says. “There is absolutely no new scientific information in this analysis.”
Neurologist Robert I. Henkin, MD who directs the Taste and Smell Clinic in Washington, D.C., believes zinc-based nasal remedies can cause loss of sense of smell.
But he agrees that little scientific evidence exists to prove it.
“The most frequent cause of smell loss is the common cold,” he tells WebMD. “The role these zinc-based products play in initiating or exacerbating this condition remains very difficult to ascertain.”