Droopy eyelids develop after Botox injections represents a rare complication. The lid levator muscle hold the lids in their normal position. If just a little Botox ends up in this muscle, the lids will go down just a bit.
Brow droop usually results from over-relaxation of the frontalis muscle in the pursuit of erasing horizontal forehead wrinkles. Sufficient action of the frontalis muscle needs to be maintained in order to keep proper brow position. This is one reason why in some people horizontal forehead lines that are just above the eyebrows will remain after propper Botox treatment. Brow droop can sometimes be improved with strategically placed additional Botox.
Longevity of these side effects depend on the amount of Botox present in the “wrong” muscles and may be anything from 4 to 16 weeks.