. Some patients encounter a slight headache for the initial 24 hours after the injections to the forehead area, especially after their initial treatment. Minor bruising on the injected area can also occur. In extremely rare cases, excess Botox can cause droopy eyelids, a problem known as ptosis. It is not likely to happen when the treatment is done by a professional cosmetic surgeon and will gradually fix itself when the Botox wears off. If you encounter drooping eyelids, you should notify your surgeon. Although very unlikely, a tiny portion of patients may experience an severe adverse reaction to Botox.