Topically applied glycyrrhizic acid causes hair removal in rats.

Context: Anecdotic reports from Turkmenistan suggest an epilatory effect of sweet licorice extract after topical application. Objective: This study examines hair removal after topical application of glycyrrhizic acid, the main compound of sweet licorice. Materials and methods: An aqueous solution containing 15% of the ammonium salt of glycyrrhizic acid, 10% urea, and 20% ethanol was topically applied two times per day on the neck areas of Wistar rats using a toothbrush. Results: After 3 d, 20-30% of the treated areas were free of hair. After treatment for 6-12 d, 90-95% of the hair was gone. Clinical as well as immunohistological examinations showed no signs of inflammation even after long-term treatment for more than 9 months. Interestingly, long-term treatment reduced the regrowth of hair of about 20%. Examination by scanning electron microscopy showed a smoothed hair cuticle that might facilitate detachment of the hair shaft from the follicular wall. Discussion and conclusion: Our findings suggest glycyrrhizic acid as an interesting molecule for treating hypertrichosis in humans.