Helsinki, Finland—Drugstores sell a lot of zinc acetate lozenges claiming to reduce the duration of the common cold. But do they really work and how effective are they when patients also have allergies?

A meta-analysis published recently in the British Journal of Clinical Pharmacology answered those questions, suggesting they can reduce cold duration by several days.

Researchers from the University of Helsinki collaborated with colleagues in the United States to review three randomized, placebo-controlled trials in 199 patients, mostly females between 20 and 50 years old and a third with allergies. The study sought to determine whether the allergy status and other characteristics of common cold patients would modify the effects of zinc acetate lozenges.

Results indicate that use of zinc acetate lozenges reduced cold duration by an average of 2.73 days after one-stage of meta-analysis and 2.94 after two stages. That was compared with the 7-day average duration of colds in the three trials.

Study authors note that the effect of zinc lozenges was not modified by allergy status, smoking, baseline severity of the common cold, age, sex, or ethnic group.

“One study indicated that zinc lozenges might be more effective for common cold patients with allergies, but we showed that the efficacy is the same for those with and without allergies,” said lead author Harri Hemila, MD, PhD, who added, “Common cold patients should be encouraged to try zinc acetate lozenges not exceeding 100 mg of elemental zinc per day for treating their colds.”

“Since the effects of zinc acetate lozenges were consistent between the compared subgroups, the overall estimates for effect seem applicable over a wide range of common cold patients,” the study concludes. “While the optimal composition of zinc lozenges and the best frequency of their administration should be further investigated, given the current evidence of efficacy, common cold patients may be encouraged to try zinc lozenges for treating their colds.”

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