Botulinum toxin type A (BoNT-A) (Botox®, Myobloc™, Dysport®, Xeomin™) is a naturally occurring toxin produced by the Clostridium botulinum bacterium. Botox A and Dysport, the commercially available forms of botulinum toxin, are purified for medical use. They work by blocking nerve signals from the brain to the muscles resulting in a temporary type of paralysis, which results in a weakening and relaxing of the muscle(s). BoNT-A is administered in tiny amounts, by injection, to a targeted area. Its full effect is generally seen between three and seven days after injection, with results lasting between three and four months, at which point the effects begin to fade and the original muscle contractions return. Many people opt or repeated treatments, which can, over time, result in thinning of the affected muscle, making the effects longer lasting. BoNT-A was approved as Botox by the FDA in 1989 for the treatment of blepharospasm and strabismus, and in 2002 it was FDA approved to treat moderate to severe lines between the eyebrows, also called glabellar lines. Today, BoNT-A is used routinely in numerous cosmetic procedures. Side effects are typically minimal and temporary. Serious and rare adverse effects include problems swallowing, speaking, or breathing, due to weakening of associated muscles, and can be severe. People at greatest risk for serious adverse effects often already suffer from some of these types of problems before they receive BoNT-A. Allergic reactions have also been reported with BoNT-A, and can include itching, rash, red itchy welts, wheezing, asthma symptoms, or dizziness or feeling faint. If you experience any of these during or following treatment tell your doctor immediately. The safety of BoN-A injections in pregnant and nursing women has not been established, though there is evidence that it does not cross the placenta. Whether it is secreted in breast milk has not been substantiated. However, so little gets into the circulation that the tiny amounts to which a healthy breast-fed infant might be exposed would not pose any likely risk.