Probably the most widely used product in aesthetic dermatology is botulinum toxin. Long known as a potent muscle relaxant, it has a large scope of application such as in the treatment of wrinkles caused by muscular hyperactivity or also for treatment of excessive sweating (hyperhidrosis). Botulinum toxin has been an approved drug for many years and is widely used beyond the boundaries of aesthetics and dermatology. In neurology it has been used for decades, for example, to relieve muscle spasms. Contrary to frequent voices in the tabloids, etc. it is one of the most actively studied substances in the world. Properly applied, it is a very safe drug. After local application of a pain-relieving ointment containing lidocaine, botulinum toxin is applied with extremely fine needles directly into the muscle. In many people, the prominent pronounced frown lines are a result of excessive muscle activity in the forehead muscles or can also arise from habit. The application of botulinum toxin here is ideal because it not only lowers the tone of the overactive muscles, but also leads to a slight shrinking of the muscle, a so-called “hypotrophy”. Immediately after application there may occur a slight reddening and swelling at the injection sites, which disappears within one or two days in most cases. The duration of action of botulinum toxin varies individually, but usually lasts about 4 to 6 months. In general, the treatments become less frequent with the number of sessions.