Botulinum toxin — Botox

Botulinum toxin (commonly known as Botox) is an injectable medication that interrupts nerve signals to muscles, causing controlled muscle relaxation. It is used for dynamic wrinkles on the forehead, frown lines, crow's feet; to slim the masseter muscle; and to reduce muscle contractions in the chin and neck. The effects become noticeable after 5–14 days and last for 3–4 months before muscle activity returns.

Medically reviewed by BS.Ths.CKI Kim Kha — BonBoz Clinic

Mechanism

Botulinum toxin type A prevents the release of acetylcholine at the neuromuscular junction, causing the injected muscle to relax as it no longer receives contraction signals. The skin above becomes smooth, eliminating dynamic wrinkles; in the case of hypertrophied masseter muscles, the muscle activity decreases and gradually shrinks after a few weeks. The effect is temporary as the nerves regenerate new endings after 3–4 months.

Common Injection Areas

Frown lines (number 11), horizontal forehead wrinkles, crow's feet, bunny lines, slight eyebrow lifting, orange peel chin, lifting the corners of the mouth, jawline slimming (masseter muscle), neck bands, and reducing underarm sweating. Each area has its own dosage and injection points; incorrect points on the forehead can cause eyebrow droop, while incorrect points at the outer corners of the eyes can lead to uneven smiles.

Why Should Dosage Be Individualized?

Muscle strength, skin thickness, expression habits, and the presence of drooping eyebrows or eyelids vary from person to person. A standardized dosage can lead to a frozen appearance or cause eyebrow droop in individuals who need forehead muscle function to open their eyes. The doctor assesses the muscles during movement, administers a lower dose during the first session, and adjusts after 2 weeks if necessary.

Risks to Be Aware Of

Bruising, mild pain at the injection site, transient headaches; temporary eyebrow or eyelid droop when the toxin spreads to the wrong muscle (2–6 weeks), uneven smiles, dry eyes or tearing, temporary weakness of the masseter muscle when chewing hard foods, and rarely, antibodies may develop that reduce response when injected too frequently. Most side effects resolve on their own as the toxin wears off.

At BonBoz

A cosmetic dermatologist conducts a direct examination, assesses muscle movement, and checks the eyebrows and eyelids before injecting the forehead, using registered products, individualized dosages, and mapping injection points for future adjustments. The doctor performs the injections personally; a follow-up appointment is scheduled after 2 weeks for any necessary adjustments.

How is it performed?

No need for anesthesia or just surface anesthesia. The doctor marks the injection points according to an individual diagram, prepares the medication at the correct concentration, and injects each point with a very fine needle into the targeted muscle with a calculated dose, applying gentle pressure to stop any bleeding. Duration is 10–20 minutes; you can go home right after.

Before the procedure

Assessing muscle function during movement, including the eyebrows and eyelids, is essential for understanding the patient's condition. It is important to inquire about their neurological and muscular history, current medications, and pregnancy status. Additionally, patients should discontinue anticoagulants and alcohol 24–48 hours prior to the procedure. Finally, ensuring a thorough cleansing of the injection area is crucial for optimal results.

After the procedure

Avoid lying face down, rubbing the injection area, steam baths, heavy exercise, and alcohol for 24 hours. Results will be noticeable after 5 to 14 days. Schedule a follow-up after 2 weeks for adjustments, and repeat the procedure every 3 to 4 months when the muscles start to regain activity.

Possible risks — your doctor explains them before treatment

Bruising, injection site pain, transient headache
Temporary eyelid droop if the medication spreads incorrectly
Asymmetrical smile, stiff expression if the dose is high
Dry eyes or temporary tearing
Temporary chewing weakness (masseter muscle)
Reduced response due to antibodies when injected too frequently (rare)

Who should NOT have this?

Patients who are pregnant or breastfeeding should avoid this treatment.
Individuals with neuromuscular diseases (such as myasthenia gravis, ALS, etc.) are contraindicated.
Those with an allergy to any component of the medication should refrain from using it.
Patients with a skin infection at the injection site must not proceed with the treatment.
Currently using aminoglycosides or medications that affect neuromuscular transmission should avoid this procedure.
Do not expect Botox to eliminate deep static wrinkles on its own.

BS.Ths.CKI Kim Kha

Aesthetic Dermatology

Graduated as a General Practitioner — Tay Nguyen University (2018)
Specialist Level I in Dermatology — Pham Ngoc Thach University of Medicine, degree awarded in 2025
Medical Practicing Certificate No. 009784/ĐL-CCHN — Issued by the Department of Health of Dak Lak Province on 15/10/2021
Over 8 years of experience in aesthetic dermatology practice (since 2018), including over 4 years of practice with an official Medical Practicing Certificate
Primary Specialization in Plastic and Reconstructive Surgery; Certificates in Dermatological Procedures & Minor Surgery, Microsurgery, and Lasers & Light Therapies in Dermatology
Certificates in Dermal Fillers, Botox, and Thread Lifts; Certificates in Emergency Resuscitation and Infection Control
Formerly practiced at the Aesthetic Dermatology Unit — Post and Telecommunications General Hospital (2019–2021) and Venus Sunrise Clinic (2022–2024) before joining BonBoz Clinic (2025)
Former lecturer in Aesthetic Dermatology Theory at Ana Aesthetic Training School (2018–2019)
Over 5,000 clinical dermatology cases treated

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Frequently asked questions

How long does Botox last?

Typically 3–4 months; for the masseter muscle, 4–6 months. Regular injections can extend the interval between sessions as the muscle weakens over time.

How long until results are visible?

Muscle relaxation begins after 3–5 days, most noticeable between days 10–14.

Does Botox make the face stiff?

With a personalized dosage and preserving some muscle function, you can still express emotions; stiffness occurs with high doses and unnecessary multiple injection sites.

Is Botox toxic?

The dosage used in aesthetics is very small compared to toxic levels, with effects localized to the injection site; it has been used in medicine for decades with registered products.

Will wrinkles worsen if I stop injections?

No. The muscles will function as before; many people notice lighter wrinkles because the skin hasn't been creased during the injection period.

How is Botox different from fillers?

Botox relaxes muscles causing dynamic wrinkles; fillers add volume or address static wrinkles. The two are often combined for different areas.

Does injecting Botox into the masseter make the cheeks hollow?

The masseter muscle gradually shrinks, creating a more defined jawline; hollow cheeks can occur with high doses in individuals with a thin face. The doctor adjusts the dosage based on muscle thickness and facial structure.

What to do if eyelids droop after injection?

This is temporary, lasting 2–6 weeks; there are eye drops available to help lift the eyelids slightly. Inform your doctor to note this and avoid that injection site in the future.

Do I need to take time off work after Botox injections?

No; you can go back immediately, and light makeup can be applied after a few hours, avoiding rubbing the injection area.