Horny goat weed is the common name for the plant known as Epimedium, which is used in traditional Chinese herbal medicine as a tonic, an aphrodisiac, and an antirheumatic agent. It also goes by the names Herba epimdii, yin yang huo, fairy wings, and rowdy lamb herb. While over 200 compounds have been identified in horny goat weed, the main bioactive constituents appear to be flavonoids, of which icariin is the most well-studied.[1] Icariin is also the main active ingredient in horny goat weed supplements.
Horny goat weed appears to have anti-atherogenic, anti-inflammatory, antiviral, and immune-modulating effects, though most of these mechanisms have only been investigated in research animals and in vitro.