Now some doctors believe the toxin can actually treat depression.
"The whole theory, it is not about how you look. It's everything to do with how the muscles of the face actually interact with your brain," explains Dr. Eric Finzi.
Dr. Finzi has been working with botox for years.
He says it's an old theory formed by charles darwin, who believed that a person's facial expression influences their mood.
"Whatever muscles you express on your face actually feed back to your brain and your brain feels the emotion," he says.
Dr. Finzi put the theory to test in 2006.
He looked at ten people, all clinically depressed.
He gave them one botox treatment in the muscle between the eyebrows, called the corrugator.
Finzi says that muscle, also known as the frowning muscle, activates and tenses up when a person gets angry or upset.
"If you inhibit the ability of this muscle to contract, you're actually going to feel less sadness and anger. You're actually going to have more difficulty feeling the emotion because feelings are not just something that's happening in the brain," he says.
Dr. Finzi says nine of the ten people in the study said their depression went away, but returned once the botox wore off.
Now he's trying to replicate those results in a larger double blind experiment with about 60 people.
He's also working with psychiatrist Norman Rosenthal, director of Capital Clinical Research Associates.
"There are so many ways to treat depression and of course the mainstay is antidepressants. Often times these are insufficient. There are still some people left feeling depressed. So we really do need novel, innovative ways to treat depressed people," Dr. Rosenthal says..
Dr. Finzi says there is minimal risk of side effects with botox.
Most common issues are pain and bruising at the site of injection.