Poindextrose is a chemical that is emitted by geeks, dorks, and four-eyes.
Lisa discovered that this is the reason bullies pick on smart people. She used it on Nelson and he cried, because he couldn't help himself punching Drederick Tatum. Later, many scientists didn't believe Lisa, even calling her a witch. She then used salad dressing as a repellent to the chemical, making Francine tame.