Topically applied glycyrrhizic acid causes hair removal in rats.

Anecdotic reports from Turkmenistan suggest an epilatory effect of sweet licorice extract after topical application. This study examines hair removal after topical application of glycyrrhizic acid, the main compound of sweet licorice. 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. 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. Our findings suggest glycyrrhizic acid as an interesting molecule for treating hypertrichosis in humans.