Most patients suffer no adverse effects at all. Those that do tend to be temporary and quite manageable. The most commonly reported side-effect is neck pain and stiffness, often accompanied by a 'wobbly neck' sensation caused by the injections into the neck and upper shoulder muscles that cause neighbouring muscles to work harder. any Botox-related weakness, stiffness or pain tends to resolve within days to weeks. Anti-inflammatory medication can be helpful for any pain or discomfort. Avoid muscle relaxants, as these may worsen the problem. Less common side effects include a temporary drooping of the eyelid which can last a few weeks. Rarely patients may experience flu-like symptoms for a few days at most.