Glycyrrhetinic acid is a bioactive metabolite of glycyrrhizin, a compound derived from licorice root (Glycyrrhiza glabra). Licorice and its extracts have a long history of use in traditional medicine for respiratory ailments, including colds and coughs. Modern scientific research has investigated glycyrrhetinic acid and glycyrrhizin for their potential antiviral properties. In vitro studies have shown that glycyrrhizin and, to a lesser extent, glycyrrhetinic acid can inhibit replication of certain viruses, such as SARS-associated coronavirus, influenza A, and herpes viruses. The proposed mechanisms include interference with viral attachment, penetration, and replication, as well as modulation of host immune responses and reduction of inflammation.

However, most of the available evidence comes from laboratory studies (in vitro) or animal models, and there are few high-quality human clinical trials directly evaluating glycyrrhetinic acid for the prevention or treatment of common cold viruses. Some clinical studies on licorice extracts (which contain glycyrrhizin and its metabolites) suggest symptomatic benefit, but these results are not robust or consistent. Therefore, while there is a scientific rationale and some preliminary evidence for antiviral effects, clinical proof in the context of common colds is limited and does not yet support strong recommendations for its use.