Zinc supplements (frequently zinc acetate or zinc gluconate lozenges) are a group of dietary supplements that are commonly used in an attempt to treat the common cold. ^[1] Evidence of any benefit is weak, but it seems zinc may not prevent colds, but possibly reduce their length while not reducing the severity of the symptoms. ^[2] Adverse effects with zinc supplements by mouth include bad taste and nausea. ^{[1] [3]} The intranasal use of zinc-containing nasal sprays has been associated with the loss of the sense of smell; ^[1] consequently, in June 2009, the United States Food and Drug Administration (USFDA) warned consumers to stop using intranasal zinc. ^[1]

The human rhinovirus – the most common viral pathogen in humans – is the predominant cause of the common cold. ^[4] The hypothesized mechanism of action by which zinc reduces the severity and/or duration of cold symptoms is the suppression of nasal inflammation and the direct inhibition of rhinoviral receptor binding and rhinoviral replication in the nasal mucosa. ^[1]

Evidence around the effect of zinc on the common cold is weak, and insufficient to provide a basis for clinic decision making. What evidence there is, suggests zinc might not help prevent colds, does not make them less severe, but might reduce their length. ^[2]

Some lozenge formulations do not contain enough zinc to effectively reduce the lengths of colds; some of them contain ingredients that bind zinc, like citric acid, which prevent the zinc from working. ^[5]

There have been several cases of people using zinc nasal sprays and suffering a loss of sense of smell. ^[1] In 2009 the US Food and Drug Administration issued a warning that people should not use nasal sprays containing zinc. ^[1]

Excessive zinc intake may result in an unpleasant taste and/or nausea. ^{[1] [6]}

The hypothesized mechanism of action by which zinc reduces the severity and/or duration of cold symptoms is the suppression of nasal inflammation and the direct inhibition of rhinoviral receptor binding and rhinoviral replication in the nasal mucosa. ^[1] Zinc has been known for many years to have an effect on cold viruses in the laboratory. ^[7] In the arteriviridae and coronaviridae families of virus that also cause the common cold, in vitro studies found that zinc ionophores block the replication of those viruses in cell culture. ^[8]