Prompted by reports of serious adverse effects, the U.S. Food and Drug Administration is requiring label changes on all botulinum toxin products. This includes a new warning box and a Risk Evaluation Mitigation Strategy.
 
The agency received reports of botulinum toxin spreading from the area of injection to other areas of the body, causing loss of strength, muscle weakness, trouble talking, loss of bladder control, trouble breathing, problems swallowing, double vision, and drooping eyelids.

Most of the reported side effects were from children with cerebral palsy being treated with Botox for muscle spasticity, an off-label use of the drug. Cases among adults were reported from on-label and off-label applications.