Botox is a drug made from a toxin produced by the bacterium Clostridium botulinum. It's the same toxin that causes a life-threatening type of food poisoning called botulism. Doctors use it in small doses to treat health problems, including
Botox injections work by weakening or paralyzing certain muscles or by blocking certain nerves. The effects last about three to four months. Side effects can include pain at the injection site, flu-like symptoms, headache and upset stomach. Injections in the face may also cause temporary drooping eyelids. You should not use Botox if you are pregnant or breast feeding.
Food and Drug Administration
References and abstracts from MEDLINE/PubMed (National Library of Medicine)