I have had Botox twice on my forehead and on both occasions only the left side has worked. Why would this happen?

It is very common to have one side of your forehead stronger than the other, and therefore would require more Botox on the stronger side. Now that you've experienced uneven results twice, go to an expert who will customize your treatment and inject more Botox on the stronger side.

Many people have asymmetries and the left side of your forehead may require more units than the right.  Neurotoxins  such as Botox and Dysport are all catered to each patient as an individual.   Another option would be to try Dysport and see if you have a better response. Thank you so much for your question.

This is rare, I have actually never seen this. I suggest using a different product in this location or higher doses at initial treatment.  Best, Dr. Emer.

This is very unusual. Typically, this is due to either underdosing that side with Botox or injecting the product incorrectly. If it worked on one side but not the other the most likely explanation is that you need additional units on the stronger side. Your nerve endings are the same throughout the facial muscles and if Botox works on one side it will work similarly on the other side. Best.Stephen Weber MD, FACSDenver Facial Plastic Surgeon

Thank you for your question.  Muscle are asymmetric. Maybe your forehead muscles are thicker and require more units of botox.  This should of been corrected the second time,. You did not mention how many units of botox you received.  You might of been under dosed.  Maybe try a board certified injector. Best Wishes.  

Sorry to hear why one side works and not the other.  Asymmetric results often the result from asymmetry of muscle mass this requiring asymmetric dosing. I would recommend that you visit with a board-certified plastic surgeon or dermatologist who is experienced with Botox to help discuss your results in more detail.

It sounds like either a muscle was missed or you may need a stronger amount of Botox on that side.  Please consult a board certified dermatologist who has a great deal of experience with Botox for the best results.

Having one side of the muscle stronger is not uncommon, but it usually only stronger by a small degree, and you should see at least some attenuation of function, especially if this side was touched up. My guess is the muscle was missed on this side, being able to visualize muscle position 3-dimensionally within the soft tissue gives the injector far more accuracy. I would suggest trying a different office to see if same results are seen. It doesn't make sense that antibodies would attack toxin on the left , but not the right

I recommend to talk to your doctor who injected your botox. Muscles
are asymmetric and may need one more than other. Another option is that the one
who is injecting is not injecting a correct dose or when he injects he is getting
the botox some how out of you body.Dr. Nabil Fakih

There is the possibility that one side is more active than the other although in actuality the frontalis on the forehead is actually only one muscle.  Be sure that you see a board certified dermatologist or plastic surgeon who is experienced in the use of the toxin