Study Confirms Zinc Nasal Sprays Linked to Loss of Smell
Last year, the FDA warned consumers that zinc-containing intranasal sprays such as Zicam might cause a loss of sense of smell. The federal regulators cited 130 reports of anosmia among users of the products. In a new analysis, University of California San Diego professor Terence M. Davidson MD finds a confirmed link to support the avoidance of such cold remedies.
Intranasal zinc gluconate is a popular over-the-counter alternative therapy used for the prevention and treatment of the common cold, write authors in the July issue of Archives of Otolaryngology-Head & Neck Surgery. However, evidence that zinc is effective in preventing or reducing the duration of a cold is questionable, based on multiple studies.
Dr. Davidson’s analysis included 25 patients who were treated at the UCSD Nasal Dysfunction Clinic who experienced loss of smell after using zinc nasal sprays or swabs to prevent or treat colds. Along with colleague Wendy M. Smith MD, he applied the nine-point Bradford Hill causation environmental exposure criteria to assess the probability that use of the cold remedies caused the loss of smell, clinically called anosmia, or the reduction of the sense, called hyposmia.
Dr. Davidson found that many of his patients with zinc-induced smell loss reported intensely painful burning in the nose when they used the products, followed by the loss of smell within several hours.
Matrixx, the company that manufactures Zicam, has removed zinc gluconate from its nasal products. The company also admits to settling several lawsuits over the past four years brought by zinc-containing Zicam users.
But the company maintains that the products are safe, and that judges in 10 cases have found little scientific evidence to support the claim that zinc-containing Zicam nasal products caused a sense of smell. In fact, upper respiratory infections and nasal and sinus diseases are well-known causes of loss and diminished sense of smell – called viral-induced anosmia.
Dr. Davidson asserts that more FDA regulation is needed to monitor the safety of zinc-containing cold remedies. “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,” he says.
Davidson TM, Smith WM "The Bradford Hill criteria and zinc-induced anosmia" Arch Otolaryngol Head Neck Surg 2010; 136(7): 673-676.