Hello, I am Doctor HUH Jung, representative director of Ruby Dermatology Clinic.

"After getting jaw Botox, my cheeks look hollow and sunken, so people tell me I look tired."

"When I smile, one corner of my mouth doesn't lift, making my facial expression look awkward and distorted."

Jaw Botox is a relatively quick and popular procedure, but in the consultation room, I frequently meet patients complaining of side effects such as cheek hollowing or unnatural facial expressions. The masseter and lower facial contour do not consist of a single muscle; rather, the masseter, risorius (expression muscle), and salivary glands (parotid and submandibular) are intricately adjacent to one another. Without precise structural mapping tailored to each individual's anatomy and fat volume, unwanted side effects can easily occur.

Here is a breakdown of the underlying causes, precise anatomical targeting, and techniques needed to achieve a smooth lower facial contour safely.

💡 3-Line Key Takeaways

• Mechanism & Target: Botulinum toxin is precisely injected into the masseter muscle (used for chewing) and hypertrophied salivary glands (parotid/submandibular) to slim and refine the lower face contour.
• Causes of Side Effects: Cheek hollowing occurs when the toxin diffuses into the upper masseter or risorius muscle, while compensatory hypertrophy happens when injection depth is uneven across muscle layers.
• Anatomical Targeting: Accurate Safety Zone marking, multi-layer depth-controlled injection, and clear distinction between the masseter and salivary glands are key to natural results.

A. How Do Jaw and Salivary Gland Botox Refine the Facial Line?

Botulinum toxin temporarily blocks the release of acetylcholine (a neurotransmitter), reducing the volume of overdeveloped muscle and salivary gland tissue.

• Masseter Muscle Relaxation: Reduces the volume of the chewing muscle that bulges when clenching, smoothing angled jawlines into a sleek V-line.
• Salivary Gland (Parotid & Submandibular) Reduction: When enlarged salivary glands below the earlobes or jawline create a heavy, square appearance, precise injection into the glandular tissue slims down the lower contour.
• TMJ Pain Relief: Offers therapeutic benefits by relieving jaw joint tension and tension headaches caused by teeth grinding (bruxism) or jaw clenching habits.

B. Candidate Assessment (Who Benefits Most?)

1. Strongly Recommended For:

• Individuals whose jaw muscles bulge significantly when biting down on molars.
• Those with a heavy, bulky lower face due to enlarged salivary glands beneath the ears or under the jawline.
• Patients suffering from jaw tightness or headaches caused by clenching or grinding habits.

2. Requires Meticulous Custom Design For:

• Patients with minimal sub-zygomatic fat under the cheekbones (prone to cheek hollows). The upper masseter must be completely avoided, focusing strictly on the lower-posterior zone.

C. Anatomical Causes of the Top 3 Jaw Botox Side Effects

• Cheek Hollow Effect:
  • Cause: Occurs when an excessive dose enters the upper masseter (below the cheekbone) or diffuses upward. In patients with little cheek fat, losing upper muscle volume accentuates the cheekbones, creating a sunken, aged appearance.
• Awkward Smile & Mouth Asymmetry:
  • Cause: Happens when toxin invades the risorius muscle, which pulls the lip corners laterally during smiling. This prevents one side of the mouth from lifting properly, leading to an asymmetrical smile.
• "Candy-in-Mouth" Compensatory Hypertrophy:
  • Cause: The masseter has a multi-layered structure. If toxin is injected unevenly into only certain layers, the unparalyzed adjacent muscle fibers contract harder to compensate, causing a localized bulge resembling a piece of candy in the cheek.

D. Comparison: Jaw Botox vs. Salivary Gland Botox

E. Duration & Recommended Treatment Interval

• Onset of Results: Muscle weakness is felt 1–2 weeks post-procedure, with visual jawline slimming reaching its peak at 3–4 weeks.
• Maintenance Schedule: Treatments spaced 3 to 6 months apart (before muscles fully regain original strength) help maintain a sleek, stable contour long-term.

F. 🔥 Synergistic Combinations for Lower Face Contouring

• Jaw Botox + Onda Lifting / Ulthera:After reducing muscle volume with Botox, Onda or Ulthera breaks down sagging subcutaneous fat and tightens the skin onto the jawline for an enhanced V-line effect.
• Jaw/Salivary Botox + Contouring Injections:Combines muscle and gland reduction with fat-dissolving agents targeting double-chin and jowl fat for a lighter facial silhouette.

G. Clinical Insights & Practitioner Notes (Doctor HUH Jung)

Jaw Botox is not merely about administering an injection into the cheek; precise depth and location control are paramount.

Before treatment, I have the patient clench their molars to manually palpate the thickest point and upper boundary of the masseter. I mark the lower-posterior 1/3 Safety Zone below the imaginary line connecting the earlobe to the corner of the mouth, strictly avoiding the risorius muscle zone. For patients with thin skin or a high risk of cheek hollowing, I exclude upper injection points entirely and apply a multi-layer split injection technique. This delivers a slim jawline while maintaining completely natural facial expressions.

📌 [Post-Care] Precautions Before & After Treatment

• Immediate Post-Care: Do not lie down for 4 hours after treatment, and refrain from rubbing or massaging the area to prevent diffusion into adjacent facial muscles.
• Dietary Adjustments: Avoid tough or hard foods (squid, gum, jerky) for a week post-procedure to support muscle relaxation.
• Normal Responses: Mild weakness or fatigue when chewing may occur during the first 1–2 weeks; this is a temporary, normal part of muscle relaxation.