Is intranasal zinc effective and safe for the common cold? A systematic review and meta-analysis

To systematically review the evidence for effectiveness of intranasal zinc used to treat a common cold, and pool the results in a meta-analysis.

A literature search was undertaken in the Cochrane register of controlled trials, MEDLINE and EMBASE databases. Inclusion criteria were randomised placebo controlled trials in patients with a common cold.

Five studies were found. Three were relevant to the issue of treatment of common colds with intranasal zinc and the results were combined in meta-analysis. High doses of intranasal zinc preparation (2.1 mg zinc/day) were reported in two studies to shorten the duration and reduce the symptom severity of common cold in healthy adults, when started within 24 to 48 hours of onset of illness. A lower dose study (0.044 mg zinc/day) found no benefit in resolution, but did report a significant improvement in symptoms at day 1 and day 3. Combining the three studies, the relative risk for benefit at day 3 was 0.62 (95% CI 0.18 to 2.19) (random effects). There were no studies with children. There were no significant harms reported.

Results from individual trials suggest some benefit from zinc for symptoms of a common cold, at least in adults. Poolingthe results for symptom relief at day 3, in a conservative meta-analysis, suggests a non-significant benefit. Unquantified concerns about permanent anosmia followingthe use of intranasal zinc may mean that the issues raised will never be scientifically resolved.