Botulinum toxin is a biological poison. The effects of the poison lead to the paralysis of muscles and sweat glands around the injection area. We really use the adverse affect of the toxin to get the desired effect. Therefore, precise knowledge of skin anatomy is very important in order to relax the desired muscles. Incorrect injection techniques could lead to undesired paralysis. Because the effect of the toxin is limited (6 to a maximum of 9 months), the adverse affects are also time-limited.