How can eye ptosis as an adverse reaction from a botulium injection?

Paralysis: Botox is a paralytic agent. If given in the right area, a muscle is rendered inactive (paralyzed). Same if injected over a nerve. If Botox is outside the are intended, untoward consequences can occur. If given near the nuscle or nerve controlling the raising or lowering of the eye lid, then it will droop (ptosis). Get Botox from a reputable dispenser/practicioner.

Different causes: Botox produces paralysis in any muscle injected. Beside the direct effect on the upper eyelid muscle that can produce a temporary droop, in many cases when Botox is injected in the forehead area to smooth down the wrinkles, it can produce a droop of eyebrow and consequently a droop of the eyelid skin. You should use a reputable surgeon with experience with Botox to avoid most side effects.