The Effect of Glycyrrhizic Acid and Aqueous Licorice Extract on Hair Growth Retardation: In Vitro Mechanistic and Efficacy Studies in Human

This study discovered that glycyrrhizic acid (GA) and aqueous Glycyrrhiza glabra L. extract (GE) significantly inhibit stem cell-related pathways in dermal papilla cells (DPCs), which are crucial for hair growth. Both GA and GE treatments led to a marked decrease in clonogenic growth, stem cell markers, and the suppression of the Akt/GSK3 beta pathway, resulting in reduced b-catenin levels and down-regulation of stem cell transcription factors Oct-4, Nanog, and Sox2. They also reduced epithelial-mesenchymal transition (EMT) markers ZEB1, Snail, and Slug. The study confirmed these effects in primary DPCs from human hair follicles. In vivo studies with 15% w/w GA and GE gels, which remained stable and non-irritating over 30 days, showed significant reduction in underarm hair growth in 22 volunteers after 14, 21, and 28 days, with the GA gel being more effective than the GE gel. Lower concentrations of 7.5% w/w GA and 10% w/w GE gels also significantly reduced hair growth without irritation and were comparable in effect to the higher concentration gels. These results suggest GA and GE could be used to suppress unwanted hair growth.