Some common side effects include mild bruising or swelling at the injection site, which usually resolves within a few days. There may be slight asymmetry in some cases, where BOTOX affects one side of the face more than the other, but this can typically be corrected with a follow-up treatment. There’s also a rare possibility of drooping or weakness around the mouth, although this is temporary and fades as the BOTOX wears off. Some patients might experience mild headaches or flu-like symptoms, but these usually subside quickly. Additionally, some individuals may have an allergic reaction to BOTOX, leading to redness, itching, or swelling at the injection site.