Nasal irrigation with Glycyrrhiza glabra extract for treatment of allergic rhinitis - A study of in vitro, in vivo and clinical trial

Ethnopharmacological relevance: Glycyrrhiza glabra, a family of licorice and a traditional Chinese medicine with sweet taste and favorable smell, has anti-inflammatory, anti-allergic and immunomodulatory functions. Aim of the study: We developed a licorice extract (LE) by using glycyrrhiza glabra and administered it through nasal irrigation to treat allergic rhinitis (AR). Materials and methods: LE was prepared into extract powder, and the anti-inflammatory effect of the LE was evaluated by calcium ionophore-induced activated mast cell model (in vitro). Then, local passive anaphylaxis assays were applied to investigate the anti-IgE-mediated allergic reaction of the LE in mice (in vivo). A developed LE was administered through nasal irrigation to treat AR in clinic settings. A total of 60 participants diagnosed with AR were included in this clinical trial; they were randomly assigned to three interventions: licorice nasal irrigation (LNI), corticosteroid nasal irrigation (CNI), and saline nasal irrigation (SNI). They performed nasal irrigation once a day for 1 month. Both subjective questionnaires (22-item Sino-Nasal Outcome Test [SNOT-22] and visual analog scale [VAS]) and objective examinations (acoustic rhinometry and nasal endoscopy) were used for effectiveness assessments. Results: All three interventions could improve SNOT-22 scores, but the effects of LNI and CNI were more significant. According to VAS scores for nasal blockage, rhinorrhea, sneezing, nasal pruritus, postnasal discharge, and olfactory disturbance, the effect of LNI was superior to those of CNI and SNI. The results of rhinometry revealed that LNI significantly improved nasal resistance. Endoscopic analysis showed that both LNI and CNI, but not SNI, could significantly improve turbinate hypertrophy. Moreover, the best procedural comfort was found for LNI, which had no side effects or complications during the trial Conclusions: LNI is a natural, safe, and innovative therapy that can effectively treat AR. Its effect is superior to those of CNI and SNI, and it has greatly improved procedural comfort.