The herb's only known planet where it grows is M6H-491. The herb contains a chemical, which interacts with the body and causes a secretion of a pheromone, which increases the gamma activity in the prefrontal cortex - the part of the brain responsible for positive emotions. This makes everyone within close proximity to the individual become influenced by them. The herb also possesses addictive properties, as the influenced would become ill and come into withdrawal after a time of no longer receiving the pheromone. The herb can also come into a liquid form, so it could be drunk by the user.
Lucius, who was mainly an annoying man travelled to M6H-491 and found a herb. He collected some and came back to his planet. Since he was a baker, he laced the herb into his bread and when the villagers ate it, he noticed people started to hate him less. Eventually he made the herb into a liquid form and used the herb to influence his way into marrying six women, as well as making all the villagers help him in every way.
After the Wraith set an outpost on M6H-491, he desperately tried to acquire more of the herb. After he encounters the Atlantis expedition, he lulled his way to influence some of the members to risk their lives to gate to the planet and get more of the herb, which he claims was used in his medicines. John Sheppard was the only expedition member not affected, as he avoided spending much time with Lucius and his cold prevented the herb's essence from getting into his system. Eventually Sheppard and Carson Beckett- Sheppard having abducted Beckett and taken him to the mainland to give him time to 'detox' from Lucius's presence- were able to discover the truth and developed a serum that effectively neutralised the herb, ending Lucius' plans. After the villagers discovered what he had done, they banished him to another planet. Rodney McKay kept a few samples of the herb and tasted one for research purposes, causing Sheppard to be affected and willingly clean McKay's quarters for him (Sheppard would be the only expedition member affected as he did not need to take the serum before and was now over his cold), but Elizabeth Weir and Beckett demanded that he burn the rest immediately. (SGA: "Irresistible")