Effect of the zygomaticus muscles, major and minor, injected with Botox? Is there a safe amount without affecting the smile?

Dear ashlibug,Unless you have a smile asymmetry, I would advise against injecting those muscles. As a plastic surgeon with years of expertise performing facial surgery, I can tell you those muscles are critical for having a full and symmetric smile. In addition, due to their depth and anatomy it is very difficult to provide a safe, isolated dose. If you decide to proceed, make sure your injector has appropriate qualifications, such as board certification by the American Board of Plastic Surgery. You want someone with extensive and real life experience in facial anatomy. Good luck!Nirmal R. Nathan, M.D.Certified, American Board of Plastic SurgeryMember, American Society of Plastic Surgeons

The zygomaticus muscles cannot be injected with Botox without affecting the smile. I'm not sure what you are trying to achieve by injecting these muscles but in the vast majority of patients getting Botox/Dysport treatment, these muscle should not be injected. 

In a vast majority of patients botox should not be used to inject the zygomaticus muscle group. It will only create problems. Good luck from New York City

I am not sure what your treatment provider is trying to achieve by injecting the zygomaticus major and minor muscles. Any weakening of these will cause a droop in the corner of the mouth.  These can be treated in isolated cases for major asymmetries, but to the best of my knowledge, it is best to avoid injecting them.