Botulinum toxin has been FDA-approved and widely used for a long time, and is very safe. As with any medical procedure, there may be some side effects. Some patients experience temporary redness and swelling at the injection site, but this is rare. An inexperienced injector may overdo the dose which can result in arched eyebrows or similar effects. This is why it is important to receive injections from an experienced plastic surgeon or injector nurse.