Zicam’s main ingredient for treating the cold symptoms is zinc. Laboratory test-tube experiments showed that high levels of zinc may curb the growth of cold viruses and boost production of infection-fighting substances.
However, one purported side effect to the use of zinc nasal sprays is loss of the sense of smell. Last year Zicam makers Matrixx Initiatives settled 340 lawsuits for $12 million brought by consumers who claimed the product damaged their sense of smell. Matrixx said the agreement was not an admission of liability but simply an effort to end the litigations. Matrixx also issued a press release in 2004 testifying to the effectiveness and safety of their flagship product.
Zicam contains zinc, and studies on animals and case reports showed that nasal zinc may possibly cause the permanent loss of smell. The most often referred study in 1938 used a concentrated zinc sulfate, and Zicam’s formula contains zinc gluconate.
There is no question that Zicam relieves cold symptoms faster. The main concern is then in its side effects.
I found this Consumer Reports article (January 2007) leading on towards the negative:
Zicam: Safe cold cure?
“Most cold medicines only treat cold symptoms,” but Zicam Cold Remedy “shortens the duration and severity of the cold,” says the Web site for this zinc-based nasal gel. Does Zicam, which costs $11 to $12 for about a week’s supply, really work–and is it safe?
Test-tube studies have shown that high levels of zinc might curb the growth of cold viruses and boost production of infection-fighting substances. But only about half the clinical trials we looked at for nasal zinc have found that it shortens or eases a cold.
More important, studies with animals and case reports suggest that nasal zinc may cause loss of smell, possibly permanent. Last year we unearthed more than 200 complaints to the Food and Drug Administration about an impaired sense of smell, taste, or both after using zinc nasal products. And about 340 consumers have sued Matrixx Initiatives, the maker of Zicam, claiming loss of smell. Last January the company agreed to settle almost all outstanding lawsuits without admitting fault. Matrixx’s promotion of Zicam is being investigated by the Federal Trade Commission, which regulates product advertising.
Oral zinc is probably safe if you take less than 40 milligrams a day. But the evidence on its efficacy is also mixed.
CR’s take. The possible risk posed by nasal zinc outweighs any benefit. it’s not clear whether oral zinc is worth taking for colds.
Scopes also wrote their take on Zicam here.