Botox Lasts 4 Months
Generally, you can expect your Botox (or Dysport or Xeomin) to start working within 4-10 days and to last 4 months. However, I have found over the years that there is a moderate amount of variation to this number. I have had patients tell me that it started to work the very next day. I do believe that if it has not started to work in 10 days, then you will need another dose. Rarely, but it has definitely happened, that some patients are resistant to Botox and it just does not work on them. I would always try a second dose of Botox before concluding that it does not work.
It is important to remember that depending on what area is injected, there will almost certainly be some movement and that this is OK. However, the movement will be very much reduced.
It is important to remember that Botox decreases the lines due to movement. It will not change the fine lines in your lower eyelid. However, the deep furrows between your eyes, will gradually get less and less deep, if you do Botox religiously for a year or more. They will not go away with just one session, if they are present even when you are not frowning.
I personally like my patients to come back every 3.5 months. Why? The analogy that I share with my patients is that if you put your leg in a cast for 4 months and then go to the gym for a few weeks and then go back in the cast for 4 months and you keep doing this for a year, your leg muscle will be a little bit smaller than the normal leg. However, if you put your leg in a cast for a year straight, the leg muscles will atrophy and will be much smaller.
What does this have to do with Botox?
If I keep injecting your muscles (eg the glabellar area which is the area between your eyes) before it has a chance to recover, these muscles will atrophy. I have found that after a year of doing this, frequently (not always though) many patients will require fewer units to get the same result. This means instead of needing 20 units in the glabellar area, you may need only 10-15 units. Sometimes it can also last longer too.