Licorice in the Treatment of Acne Vulgaris and Postinflammatory Hyperpigmentation: A Review

Clinical advantages of licorice (Glycyrrhiza spp.) have been investigated for several years. It has been traditionally used for a variety of disorders. Different constituents with various characteristics have been isolated from Glycyrrhiza spp. extracts. This review aimed to summarize the current knowledge on the pharmacological efficacy and safety of licorice extract constituents to treat the pathophysiology of acne vulgaris (AV) and the associated postinflammatory hyperpigmentation (PIH). Anti-androgenic, antimicrobial, anti-inflammatory, antioxidant, depigmenting, and skin-turnover-accelerating properties have been identified for licorice extract which could be effective against AV and PIH through multiple pharmacological mechanisms. The active compounds responsible for these pharmacological activities, molecular mechanisms, safety profile, as well as the in vitro, in vivo, animal, and clinical studies are discussed. Licorice extract possesses broad-spectrum activity and could be considered as an effective and safe option in the treatment of AV and its associated PIH. However, evidence-based clinical trials are required to prove its efficacy as well as safety. We hope this paper can provide new insights for further studies, particularly large controlled clinical trials.