BOTOX® Cosmetic acts by paralyzing the muscles that cause dynamic wrinkles. It is injected into the muscle and prevents the muscle from contracting by blocking the transmission of nerve impulses. Because the muscle cannot contract, the wrinkle relaxes. Mainly used for dynamic wrinkles in upper third of face, but also used for other face/neck areas, migraine headaches, and excessive underarm sweating. Not as effective on static wrinkles—those are better treated surgically or with dermal fillers.