Cnidium monnieri is an herb naive to China. Cnidium has been used for hundreds of years in traditional Chinese medicine for skin problems and as a libido booster. Cnidium is most often used in combination with other herbs for libido enhancing.
Cnidium is considered a reproductive aid and aphrodisiac.  Cnidium seeds are said to be a natural libido booster; and in the treatment of male sexual dysfunction and impotence, it apparently, helps to relax the corpus cavernosa of the penis (the chambers in the penis that fill with blood during an erection), allowing blood to flow freely and helping to produce an erection.

Cnidium is said to help increase the release of nitric oxide, a substance that is important for stronger, longer-lasting erections.  Nitric oxide activates enzymes that make the substance, cyclic Guanosine Monophosphate (cGMP), which relaxes the muscles around the genital area and allows the penis to swell.