Can Botox cause facial muscles to weaken and then result in my face sagging?

Botox doesnt cause the skin to worsen, if anything it improves the complexion due to improvement in oiliness.  The muscles can atrophy if you use it too much with too high does , which is why I do very conservative doses especially on the forehead.  Best, Dr. Emer.

If performed properly, no. The loss of elasticity we experience with aging is an issue intrinsic to the skin not the facial muscles. If Botox is used to carefully target facial muscles your face will not say or droop.