Hi Christine, it's not used to plump your lips, but it is used cosmetically to remove frown lines, especially in the forehead and between the eyes. It does that because it keepts the muscles there from contractig as they normally would. I just looked it up on wikipedia. I tell my students wikipedia isn't such a reliable source but it has gotten better since they require footnotes. Still take all info. there with a grain of salt.

Still, it's c;lear it has been used to treat various symptoms related to overly tightened facial muscles for quite a while. Which makes me feel a little better.

http://en.wikipedia.org/wiki/Botox