Facial slimming injections are only effective for large faces caused by developed masseter muscles.A large face typically stems from two causes: either bony hypertrophy of the mandibular angle, or excessive development of the masseter muscle causing protrusion on both sides of the cheeks. Facial slimming injections target the developed masseter muscle, causing it to relax, become temporarily paralyzed, and weaken its contractile force. Ultimately, the muscle atrophies due to lack of exercise, achieving the slimming effect.
Facial stiffness after treatment may result from these factors:
1. Normal reaction following proper administration. Weakened masseter muscle strength after injections can cause unnatural facial expressions—a standard injection response. This stiffness may appear within 24 hours post-treatment, peaks 7–14 days later, and typically resolves within 2–8 weeks.
2. Improper injection site. When administering facial slimming injections, the doctor must precisely inject botulinum toxin into two points on one side of the face: the first point is located at the most prominent part of the masseter muscle (confirmed and marked after observing both clenched and relaxed jaw states); the second point is positioned diagonally above the first point, at least 25px away.
Deviation at either point causes abnormal facial stiffness lasting over 8 weeks.
3. Superficial injection depth. For effective facial slimming, botulinum toxin must be injected into the masseter muscle.
If the doctor lacks a solid grasp of anatomical layers and injects Botox into the superficial muscle layer instead, it may damage the facial nerve. This can cause abnormal facial stiffness, commonly manifesting as drooling, a mouth tilted to one side, or involuntary twitching at the corner of the mouth. Such effects may persist for years.
4. Excessive botulinum toxin dosage. Generally, medical aesthetic treatments involving less than 100 units per injection are relatively safe. For facial slimming, the total dosage for both masseter muscles should not exceed 100 units.
If a doctor irresponsibly over-injects to satisfy your urgent desire for results, the abnormal facial stiffness may persist for over 8 weeks.
5. Insufficient interval between injections. To achieve optimal facial slimming results, multiple botulinum toxin treatments are permissible, but each session must be spaced at least one month apart.
If you undergo multiple injections within a single month and develop unnatural facial expressions, unfortunately, this condition may persist permanently.
6. Massaging the injection site after treatment. After Botox injections, doctors typically advise against manual massage. Massaging can cause the Botox solution within the masseter muscle to seep into adjacent facial muscles, exacerbating unnatural expressions. In such cases, normal facial expression recovery may take longer than 8 weeks.