Every drug has side effects, and Botox is no exception. Luckily, “Botox side effects are rare and temporary,” says Adam Kolker, a board-certified plastic surgeon based in New York City. Potential side effects (in just 1 to 5% of cases) include mild droopiness of the eyelid or eyebrow, which usually goes away within two weeks, slight bruising at the injection area, and headaches.  - allure.com