Botox is a formulation of botulinum toxin type A. It is derived from the bacterium Clostridium botulinum. This bacterium produces a protein that blocks the release of acetylcholine and relaxes muscles.

When injected, Botox travels through the tissues until it finds the nerve that ends on a muscle. The nerve ending absorbs the Botox, and the medication acts to prevent the nerve from firing. This weakens the muscle, and the muscle can no longer produce the facial lines.

Ultimately, the nerve ending regenerates, and the muscle regains its previous strength. This is why injections of Botox wear off and have to be repeated.

Botox works best on the upper third of the face. Forehead furrows, glabellar frown lines (between the eyebrows), and lines around the eyes (“crow’s feet”) nearly always respond favorably to Botox.

Lines around the mouth respond only about half the time. Injections around the mouth risk an uneven smile, even if the injection is properly performed. Dimples, discolorations, and sun damage do not respond to Botox.