Botox Cosmetic used in cosmetic treatments is the commercial trade name of a purified protein Botulinum Toxin Type A produced by the Clostridium Botulinum bacteria. The treatment may have some side effects, like any other medication. Skin rash, allergic reaction, localized pain and local weakness of injected muscles are the most reported botox injection side effects. If you are allergic to any ingredients in the injection or has an infection in the region where it was administered, there is a probability of botox injection side effects. Botox injections are also not recommended for pregnant or nursing women and those taking medications that can have possible interactions with botox.