What are the side effects to masseter reduction with Botox, and how long does the swelling last?

For a medium-sized female jaw, I typically use 15-20 units per side.  If the muscles are large, I will use up to 30 units per side for a female.  Men sometimes require as much as 50 units per side, since they have much more bulk.The worst, unwanted side effect is alteration of the smile.  This happens if the injection is placed too high or too anteriorly.  This can result in undesired weakening of the muscles that pull back/elevate the angle of the mouth during smiling.  Other side effects include 1) the face becoming too slim, 2) the jowls appearing more prominent because the back of the face is less bulky.There is not typically any swelling with the botox injection, unless a bruise forms.  If a bruise forms, this may take a few days to go away.One other caveat is that if the "square jawline" is due to an angular jawbone, botox will not change the shape of the jawbone.  It only softens and shrinks the masseter muscle.

Hello and thank you for your question.  Treatment dosage for large masseters vary from one person to the next, however, it can normally require 20-30 units per side. On examination I determine the amount of Botox needed by placing my hands on the patients face while having them clench using their back teeth.  This gives me a good indication of how strong their muscles are, and how much Botox they can handle, without compromising normal and necessary usage of the muscles.  After your treatment there is usually minimal swelling, some around each injection site, and some from the fluid (Botox) that is injected and is waiting to be absorbed by the muscle.  This swelling doesn't last more than a day, and usually goes unnoticed.  There is also a chance of bruising, although less likely with Botox than with fillers, but taking proper precautions can minimize this risk.  Avoiding blood thinners and alcohol 5 days before your injections can help reduce your risk.  Taking Arnica starting the day before and continuing the day of can also aid in the healing process. I advise that you seek an experienced injector who specializes in facial aesthetics and has experience treating masseter hypertrophy or TMJ for best results.  Good luck!

The most important "precaution" to take when undergoing Botox for masseter reduction is to do your homework in finding a qualified physician to perform the treatment.  A typical "moderate" dose is 50 units, or 25 units of Botox on each side.  Immediately after the procedure there typically is not any discernible difference, as the masseter muscle is so bulky to begin with that the volume of Botox does not make a huge visual difference.  With an experienced physician the main possible side effects are bruising (<5% of patients) and you may notice you become tired sooner when chewing excessively (all day gum chewing or 22 oz steak etc).