MONDAY, July 19 (HealthDay News) -- To try and lessen the
effects of the common cold, many people have turned to homeopathic
remedies, including products containing zinc.
However, a new analysis suggests that nasal gels containing zinc
and nasal swabs with zinc have most likely caused a loss of smell
in some users.
"In my practice, we started seeing people using the zinc nasal gel. They squirted it in, took a deep sniff and then had an incredibly intense burning sensation that lasted for several hours. When these people recovered, they found they had no sense of smell," explained study author Dr. Terence Davidson, director of the University of California at San Diego Nasal Dysfunction Clinic.
The loss of smell is called anosmia, and Davidson said that
people might not appreciate how significant it can be. "Most of us
take our sense of smell for granted. But, people need to take a
moment to realize how important smell is. It helps us avoid dangers
when we smell smoke or gas or rotten, spoiled food and it brings us
incredible pleasure -- think about the smell of our homes, loved
ones, food, coffee. In fact, 90 percent of our appreciation for
food comes from our sense of smell," he said.
Davidson said that some of the people affected by the
zinc-induced anosmia filed lawsuits against the manufacturers of
these products. However, there are no randomized, controlled
clinical trials that conclude a loss of smell is one of the
possible outcomes from using these products, making it harder to
Since it would be impossible, as well as unethical, to try to
conduct such a study now, Davidson and his colleague, Dr. Wendy
Smith, applied the "Bradford Hill Criteria" to 25 patients they had
seen for the sudden loss of smell after using a zinc gel
The Bradford Hill Criteria were developed in 1965 by a
statistician who wanted to establish a causal link between tobacco
smoking and lung cancer. The nine key criteria necessary to find a
causal link include: strength of the association, consistency,
specificity, timing, dose-response (does more of the substance make
the problem worse?), biological plausibility, biological coherence,
experimental evidence and analogy.
"Dr. Smith and I applied the criteria to zinc-induced anosmia and conclusively show that nasal zinc was the cause of the subsequent loss of smell," said Davidson.
The finding is published in the July issue of the
Archives of Otolaryngology, Head and Neck Surgery.
In addition, the efficacy of these products in reducing cold
symptoms is "questionable," according to the study.
The patients seen by the researchers had a permanent loss of
smell, but Davidson said there are likely people who have had
lesser degrees of damage from these products as well.
Homeopathic remedies like nasal zinc aren't subject to the same
rules and regulations that prescription and over-the-counter
medications are. However, in June 2009, the U.S. Food and Drug
Administration recommended that consumers stop using these products
and requested that the manufacturers stop selling them, which they
did. Oral zinc products are not associated with this problem and
remain on the market.
HealthDay was unable to reach a spokesperson for Matrixx
Initiatives, a former manufacturer of nasal zinc. However, in a
press release dated June 16, 2009, William J. Hemelt, acting
president of Matrixx Initiatives, said, "It is well-understood in
the medical and scientific communities that the most common cause
of anosmia is the common cold, which Zicam Cold Remedy intranasal
gel products are taken to treat." He said that, "given the enormous
number of doses sold and colds treated," there's no cause to think
that the number of cases of anosmia reported is any more than what
might be expected in the general population. "There is no reliable
scientific evidence that Zicam causes anosmia," Hemelt
But another expert isn't so sure.
"I think this study was well-done, and I think intranasal zinc can impair the sense of smell. Does it happen all the time? No. Is it a rare event? No," said Dr. Marc Siegel, an associate professor of medicine at the New York University School of Medicine and the NYU Langone Medical Center in New York City. "The problem is that it's not FDA-regulated. If this were a prescription drug, you probably would've seen this [side effect] in the trials needed for approval," he said.
The take-home message for consumers, said Davidson, is to "be
careful about the things you put into your body. Whether it's a
drug or a homeopathic medicine, not all are safe, so be
Learn more about nasal zinc products and the loss of smell from
U.S. Food and Drug Administration.