Thank you for your question. Botox can be a very effective way to treat a jawline that is overly full. Botox will not cause the skin in that area to sag, it does not have an effect on the skin, just the jawline volume.
Thanks for your question. It is difficult to answer your question without photos. However, generally speaking Botox can be used for treating large massetter muscles (angle of the jaw) very effectively and it can give a more sleek shape ot the face for the right candidate. Best wishes, Dr Sajjadian
Effect on skin of Botox for masseter reduction
Botox for masseter reduction effectively treats the muscle that causes fullness along your jawline and the angle of your jaw (sides of your lower face) but it does not affect your skin. It will not make your skin sag, nor will it significantly "lift" the skin. It will simply reduce the volume of the lower third of your face, thereby tapering its appearance.
Botox Along The Jawline Can Give A Lift To Lower Face & The Upper Neck ("Nefertiti Lift')
Botox (as well as the other neuromodulators, Dysport and Xeomin) have been used to treat the masseter muscle, as in this case, to contour the lower face. When placed along the jawline and into the vertical cords on the front of the neck, they are also used to achieve the so-called "Nefertiti Lift." In this technique, by injecting the platysma muscle with neuromodulators in these locations, the muscle is weakened just enough to allow the muscles of the face to gain an advantage that results in upward pull on the jawline and upper neck, all of which is intended to create the ideal, chiseled profile of the famed step mother of the pharaoh King Tut.
Given the fact that Botox can be employed in this fashion, it is unlikely therefore that the sagging described relates to the Botox. More likely is that age-related loss of the volume within the fat pads of the cheeks, which can begin in a person's thirties, may be contributing to this and to the beginnings of the deepening of the nasolabial folds (smile lines).
Consultation with a board certified aesthetic core physician with experience and expertise in the use of fillers, volumizers and neurolmodulators is your best bet for determining how to proceed.
Botox to Masseter muscle cause skin sagging?
Because there are no direct attachments of the skin to the masseter muscle, the muscle does not affect the skin level and therefore would not cause the skin sag. Even injection anterior to the Masseter near the origin of the zygomaticus muscle which creates the nasolabial crease would not likely exaggerate the crease but instead lessen it. The NL fold and crease are created by the insertion of the zygomaticus into the skin so that smiling activates the muscle which elevates the skin attachment . In addition, the descent of the skin and soft tissue from the malar (cheekbone area) due to aging and laxity contribute to the depth of the crease. In addition to filler such as Juvederm in the crease and lifts which I would not recommend at your young age you might consider restoring volume to the mid face by injection of Voluma or Sculptra. This should help lessen the NL crease.
Jawline Botox helps Slim the Face
Botox along the Jawline helps soften the masseter muscle. This allows thinning of the face. You should only have these injections by an Botox expert as injections in the wrong place and lead to unwanted side effects such as asymmetry of your smile which can last for several weeks to months. This treatment will not lead to loose skin.
Botox will not stop aging
Your nasolabial crease lines will become more apparent with age, Botox does not stop the aging process. Filler might be useful in the creases. Botox will not cause your jawline skin to sag.
Botox should not cause your skin to sag it will only treat the muscle it is injected into. Sagging will occur with time as you age.
At your age, there are many elastic fibers present in your skin and your skin will rebound over any muscle or area of fat that is reduced in size. Just make sure you protect that elasticity by using sunscreens that have either mexoryl or micronized zinc oxide, and eat a healthy diet rich in antioxidants and minerals such as magnesium, copper, and zinc. You might consider applying properly-formulated creams containing Retin A, Tazarac, retinol, glycolic acid, vitamin C, green tea polyphenols, and/or growth factors recommended by your dermatologist as well, which in my experience and on the basis of my research have profound medical and antiaging benefits over time, even more so when started at a young age.
Botox To Masseters Will Not Cause Sagging Skin
Botox is common injected into the masseter muscles to shrink them. It help narrow the lower aspect of the face to improve facial balance and slenderize the jawline. The facial skin is elastic and will contract over the shrinking muscle to prevent sagging of the skin. The sagging skin you are noticing is most like a normal change in the face as one ages.
I hope this helps.