**Abstract**

Botulinum toxin is a corner stone in the facial esthetics. It has been used for decades for various medical and esthetic indications. Botulinum toxin is a neurotoxin that interferes with the transmission at the neuromuscular/neurosecretory junctions by inhibiting the release of acetylcholine. An in depth knowledge of the functional anatomy of facial muscles is required to obtain the best results of the botulinum toxin injections. In this book chapter, a detailed practical guide for the FDA approved and the off label uses of botulinum toxin in the face is presented. The recently developed new indications are listed. The lengthy experience with botulinum toxin injections has proved safety and tolerability of the procedure; however, the probable complications, and steps for their prevention and management are highlighted.

**Keywords:** Botulinum toxin, facial esthetics, Crow's feet, anti-aging, forehead lines

Botulinum toxin (BTXN) is an exotoxin produced by the anaerobic, Gram positive, spore forming bacteria; *Clostridium botulinum.* There are seven serotypes A-G. A and B serotypes are the ones currently used commercially. The toxin is 150 kDa polypeptide, formed of heavy chain and light chain bound by heat sensitive disulfide bonds and noncovalent forces. The toxin may be formulated in a simple - free from proteins - form e.g. incobotulinum or complexed with proteins as hemagglutinin and "nontoxic molecule" to form onabotulinum toxin and abobotulinum toxin [1, 2]. It is essential to keep in mind that the different types of the toxin are not similar in their biological effects and potencies [1]. The currently available formulations are unique, so their doses are not interchangeable, and the dose response curves are probably not parallel [3].
