Botox is fabulous for diminishing the crow's feet around the eyes. The effects last generally for four months in that area. There are no known side effects from these injections except local swelling or bruising. For the best cosmetic results please find a board certified dermatologist with a great deal of experience with Botox.
Thank you for your question. Long term side effects of Botox are essentially none. It is a paralytic that temporarily prevents the muscle from working at the site of injection. One of the first uses of Botox was for a disorder called Bleaphrospasm where the muscle par is the eye twitches uncontrollably. It is still used for this indication and has not seen any ill effects long term for this use.
Botox has been used for over 20 years, and has been used in the U.S. with FDA approval for about 13 years. We have yet to see any long-term problems as long as you are injected by a trained professional. When I see issues it's because of poor injection or fake Botox. So, find a trained professional (preferably a physician in a core aesthetics field) and that will start you on the right track. There is only one kind of Botox. There are other brands that are similar like Dysport and Xeomin. But all last about the same amount of time and cost the same for injections, so it's really just up to your preference.
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Botox for areas around eyes, long term risks
Botox has now been used for more than 20 years, and we have yet to see any real problems from the regular use of cosmetic botox. As long as your injector is an experienced physician such as a dermatologist, you will receive the optimal results and safety. All botulinum toxins currently last approximately 4 months, and many people report that botulinum toxins last longer with repeated treatments (similar as fillers)