For women with excessively large masseter muscles, conventional exercise methods often fail to achieve significant facial slimming. Consequently, many opt for facial slimming injections. However, some individuals experience noticeably stiff facial expressions after treatment, causing considerable anxiety.
So why do facial expressions become stiff after receiving facial slimming injections?
1. Normal reaction following proper administration
After botulinum toxin injection, the masseter muscles weaken, causing facial expressions to appear unnatural. This is a normal reaction to the injection. Such unnaturalness typically appears within a day, peaks around one week post-injection, and usually resolves within two weeks, allowing expressions to return to normal.
2. Improper Botox Placement
During injections, Botox is typically targeted at two precise points—usually where the masseter muscle is most prominent. If either point is misplaced, it can cause significant facial stiffness. This stiffness generally lasts about two months.
3. Injection too superficial
For optimal results, Botox must be injected into the muscle fascia of the masseter. If anatomical layers are not thoroughly understood and Botox is injected into the superficial muscle layer, it may damage the facial nerve. This can cause abnormal facial stiffness, with common symptoms including drooling and mouth twitching. Such effects may persist for many years.
4. Excessive Botox Dosage
Generally, injecting less than 100 units per session is relatively safe. Even when treating both masseter muscles, the total dosage should not exceed 100 units. Injecting more Botox to meet patients' expectations for slimmer faces can also cause abnormal facial stiffness.