The onset of muscle paralysis by Botox injections is usually at full effect about 6 or 7 days after the injections. Typically, you will see a change in 3-4 days and feel a little tightness of the overlying skin. When you try to frown or move the area of the face that was treated, you can tell the effect in the mirror. Some patients report a bit of muscle slow down as if it is working as soon as 1 day after the injection.
Botox should last around 3-4 months. If you are routine about getting it you may be able to space treatments out even further. There is no statement really on the limit to how long you can keep getting Botox, although safety and efficacy data suggest that this is a predictable and safe method to treat certain areas of the face over time by qualified and trained professionals. Botox has been used in other fields besides cosmetic surgery for many, many years, and is FDA approved for specific cosmetic purposes now.
