Botulinum toxin: when, how and where?

Botulinum toxin is one of the most widely used procedures in dermatology and aesthetic medicine, but also one of the most confusing. Knowing when it’s indicated, how it works, and where it can be applied helps in making safer, more realistic, and well-informed decisions. It’s not just about smoothing wrinkles: it’s an injectable medication that requires medical evaluation, precise technique, and clear expectations.

Summary in 60 seconds

• Botulinum toxin is an injectable medication that temporarily relaxes specific muscles.
• In dermatology, it is mainly used to smooth wrinkles related to facial movement and to treat excessive sweating, especially underarm sweating, when other measures are not sufficient.
• “Botox” is a brand name; the general medical term is botulinum toxin . It is not a filler, it does not increase volume, and it does not “erase” all types of wrinkles.
• Its effect usually begins to be noticeable in a few days, reaches a more complete result around 10 to 14 days in many people and usually lasts around 3 to 4 months, although it can vary.
• Safety depends on three factors: authorized product, proper medical evaluation, and correct technique. Recent FDA and CDC alerts about counterfeit or mishandled products reinforce a key point: it should not be applied at home, in makeshift settings, or by unlicensed and untrained individuals.

What is it? Simple definition

Botulinum toxin is a purified medical substance that, in controlled doses and administered by injection, temporarily reduces the contraction of certain muscles. In facial aesthetics, it is used to treat wrinkles that appear or worsen with repetitive facial expressions: frowning, raising the eyebrows, smiling broadly, or contracting the chin. ASPS sf

It’s not a «filler.» Fillers add volume or support; botulinum toxin acts on muscle activity. That’s why it works best when the main problem is repetitive movement, not when the line is primarily due to sagging, volume loss, or significant sun damage. BAAPS sf

What is it for?

In dermatology and aesthetic medicine, its best-known uses are:

• Lines between the eyebrows, associated with the gesture of frowning.
• Crow’s feet, related to smiling or tightly closing the eyes.
• Horizontal lines on the forehead.
• Neckbands, on selected individuals.
• Chin with a «cobblestone» appearance.
• Gummy smile, bruxism or masseter hypertrophy in selected cases.
• Excessive underarm sweating when topical treatments do not effectively control the problem.

Regulatory approval varies by country, product, and area. Some areas are commonly used by experts, but may be considered «off-label» depending on the location. Therefore, the inquiry should clarify what will be treated, with which product, whether the use is approved locally, and what alternatives exist. Padda 2023 , Sundaram 2016

When should you consider it?

It makes more sense to consider this when the wrinkle appears primarily with movement. For example, if deep lines form between the eyebrows when frowning, or if pronounced lines appear around the eyes when smiling. In these cases, partially relaxing the muscle can soften the expression without eliminating it, provided the technique is conservative and personalized. AAD sf

The decision shouldn’t be based solely on age. The idea of «preventive toxin» has been heavily used in marketing, but the actual decision should depend on anatomy, muscle strength, wrinkle type, medical history, expectations, and risk tolerance. A young person doesn’t need botulinum toxin by definition; an older person may need other approaches if the primary problem isn’t muscular.

The procedure should be postponed or avoided if there is pregnancy or breastfeeding, infection or inflammation in the area, a history of certain neuromuscular diseases, significant facial weakness, a known allergy to any of the product’s components, or use of medications that may interfere with neuromuscular transmission. Individual evaluation by a specialist physician is mandatory. BAAPS sf , Cleveland Clinic 2022

Where does it apply?

The most common areas on the face are:

Between the eyebrows: aim to soften the expression of anger or tension. It is one of the classic areas.
Forehead: requires special care, because treating it without considering the eyebrows can cause heaviness or drooping of the eyebrow.
Crow’s feet: you can soften side lines when smiling, without losing your smile if you do it right.
Chin: It is used in some cases to reduce the appearance of uneven or contracted skin.
Masseter muscle: may be indicated in muscle hypertrophy or certain patterns of mandibular tension, with appropriate medical evaluation.
Neck: Platysmal bands may improve in selected individuals, but this area requires experience due to the risk of cervical weakness or difficulty swallowing.
Armpits: In axillary hyperhidrosis (excessive sweating), the application is on the skin, not on facial muscles.

The international consensus on facial aesthetics emphasizes that areas are not treated as isolated points: muscles interact with each other. Proper application must respect the patient’s anatomy, muscle strength, pre-existing asymmetries, and desired outcome. (Ascher 2024 , Sundaram 2016)

How does it work?

A simple way to understand it: the muscle moves because it receives a «command» from the nerve. Botulinum toxin temporarily reduces that signal or «command» at the treated point. By receiving less of a signal, the muscle contracts with less force, and the overlying skin folds less.

It does not eliminate skin sensitivity. The person continues to feel touch, cold, heat, or pressure in the area, because the target is not the sensory nerves but the communication between nerve and muscle .

The modern goal shouldn’t be to «freeze» all expression, but rather to modulate specific muscles. A subtle result aims for a face that appears less tense, not immobile.

What to expect?

Before

• The consultation should include medical history, medications, history of procedures, allergies, pregnancy or breastfeeding, neuromuscular diseases, bruising tendency, and expectations. It is also advisable to discuss costs, alternatives, expected duration, risks, and follow-up plan. AAD sf
• The practitioner may ask for facial expressions to assess muscle strength and asymmetries. This is normal. Clinical photographs, when taken with consent, help to compare progress.

During

• The procedure is usually performed in the office. The skin is cleaned, and small injections are administered with a fine needle at specific points. The discomfort is typically felt as brief pricks. The duration depends on the number of areas treated.

After

• Most people can resume their normal activities the same day. The AAD recommends not rubbing or massaging the injected areas and waiting before engaging in strenuous exercise to reduce the risk of the product migrating to unwanted areas. AAD sf
• The effect is not immediate. Many people notice changes within 3 to 7 days; the full result can be best assessed after about two weeks. The average duration is usually between 3 and 4 months, sometimes more or less depending on the dosage, area treated, metabolism, muscle strength, and product used. AAD sf , Cleveland Clinic 2022

Aftercare

After the application, it is wise to follow the professional’s specific instructions. In general terms:

• Do not massage or rub the treated areas on the same day.
• Apply makeup gently if the professional allows it.
• Avoid strenuous exercise during the indicated period.
• Do not manipulate lumps, red spots, or small bruises.
• Don’t look for «touch-ups» too soon: the result needs days to stabilize.
• Contact the center if any concerning effects appear, especially marked drooping of the eyelid, double vision, difficulty swallowing, or weakness outside the treated area.

There is no safe way to self-administer botulinum toxin. It is an injectable medication and must be administered by authorized, trained medical personnel using a legitimately sourced product.

Expected vs. unexpected effects

Expected and generally mild effects include brief pain, redness, minor swelling, bruising, local tenderness, mild headache, or a feeling of tightness. In reviews of cosmetic complications, most reported events are mild and transient, although asymmetries or undesirable muscular effects may occur. (Zargaran 2022 , Sethi 2021)

Unexpected effects or effects that require evaluation: significant drooping of the eyelid, blurred or double vision, difficulty speaking, swallowing or breathing, general weakness, allergic reaction, fever, progressive severe pain, discharge, spreading redness or signs of infection.

Authorized products carry warnings about the potential for dissemination of the toxin’s effects, a rare but potentially serious event. The risk increases with the use of counterfeit products, improper dosages, or application by untrained personnel. FDA 2025 , CDC 2024

Warning signs: when to seek emergency care

Seek immediate medical attention if you experience the following after application:

• Difficulty breathing.
• Difficulty swallowing.
• Slurred voice or difficulty speaking.
• Intense double or blurred vision.
• Generalized muscle weakness.
• Marked drooping of the eyelids associated with other symptoms.
• Intense pain, fever, or signs of infection in the area.
• Allergic reaction: extensive hives, swelling of lips or face, feeling of throat closure.

The CDC describes symptoms consistent with botulism as blurred or double vision, drooping eyelids, difficulty swallowing, difficulty breathing, and muscle weakness; if these symptoms occur, the recommendation is to go to the emergency room. CDC 2024

How to choose the right professional

Before getting botulinum toxin injections, it’s a good idea to ask:

1. What training and license does the person who will be administering the injection have?
2. Is the procedure performed in a suitable clinical setting?
3. What product will be used and where does it come from?
4. Is it approved by the relevant health authority?
5. Which areas will be treated and why?
6. What results are realistic in my case?
7. What risks do I face due to my medical history or medications?
8. What should I do if a complication arises?
9. Is there written informed consent?
10. Will there be a subsequent review if required?

The AAD advises patients to ask who will be administering the injections, how much experience they have, and what results they can expect. The FDA and CDC recommend confirming that the provider is licensed and trained and that the product comes from an authorized source. AAD sf , FDA 2024 , CDC 2024

Be wary of unusually low prices, home applications, «toxin parties», products without verifiable packaging, absence of a medical history, or refusal to explain what is being used.

Frequently Asked Questions

Does botulinum toxin change the face?

• It can change your expression if applied excessively or to inappropriate areas. When properly indicated and performed by a certified professional, it aims to soften specific contractions, not transform your face.

How long does it last?

• The effect usually lasts around 3 to 4 months, although it can vary. In some people it lasts less; in others, a little longer.

From what age can it be applied?

• There is no universal age limit. It should be considered in adults when there is a clear indication, realistic expectations, and no contraindications. It should not be done solely due to fashion trends or aesthetic pressures.

Does it work for all wrinkles?

• No. It works best on dynamic wrinkles, those related to movement. Lines caused by sun damage, sagging, or volume loss may require other approaches.

Hurts?

• It usually feels like brief pinches. Tolerance varies, but it is generally a procedure with limited discomfort.

Can it be done during pregnancy or breastfeeding?

• For cosmetic procedures, it’s prudent to postpone them. Data is limited, and most clinical sources advise against them during pregnancy and breastfeeding unless specifically indicated by a doctor and after individual assessment.

Can I buy it and apply it at home?

• No. It is an injectable medication. Self-administration or administration by unauthorized persons can cause serious complications, especially if the product is counterfeit, unapproved, or was improperly stored.

Bibliography and sources

• American Academy of Dermatology Association. Botulinum toxin therapy: Overview . AAD; [cited 2026 May 30] .
• American Academy of Dermatology Association. Botulinum toxin therapy: FAQs . AAD; [cited 2026 May 30] .
• American Academy of Dermatology Association. Botulinum toxin therapy: Preparation . AAD; [cited 2026 May 30] .
• American Society of Plastic Surgeons. Botulinum Toxin . ASPS; [cited 2026 May 30] .
• Padda IS, Tadi P. Botulinum Toxin . In: StatPearls [Internet] . Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Updated 2023 Nov 6 [cited 2026 May 30] .
• Sundaram H, Signorini M, Liew S, et al. Global Aesthetics Consensus: Botulinum Toxin Type A—Evidence-Based Review, Emerging Concepts, and Consensus Recommendations for Aesthetic Use, Including Updates on Complications . Plast Reconstr Surg. 2016;137(3):518e-529e.
• Ascher B, Rzany BJ, Kestemont P, et al. International Consensus Recommendations on the Aesthetic Usage of Ready-to-Use AbobotulinumtoxinA . Aesthet Surg J. 2024;44(2):192-202. doi:10.1093/asj/sjad222.
• Zargaran D, Zoller F, Zargaran A, Rahman E, Woollard A, Weyrich T, et al. Complications of Cosmetic Botulinum Toxin A Injections to the Upper Face: A Systematic Review and Meta-Analysis . Aesthet Surg J. 2022;42(5):NP327-NP336. doi:10.1093/asj/sjac036.
• Sethi N, Singh S, DeBoulle K, Rahman E. A Review of Complications Due to the Use of Botulinum Toxin A for Cosmetic Indications . Aesthetic Plast Surg. 2021;45(3):1210-1220. doi:10.1007/s00266-020-01983-w.
• US Food and Drug Administration. Counterfeit Version of Botox Found in Multiple States . FDA; 2024 May 2 [cited 2026 May 30] .
• Centers for Disease Control and Prevention. Harmful Reactions Linked to Counterfeit “Botox” or Mishandled Botulinum Toxin Injections . CDC; 2024 Dec 17 [cited 2026 May 30] .
• US Food and Drug Administration. FDA Warns Companies Over Illegal Marketing of Botox and Related Products . FDA; 2025 Nov 5 [cited 2026 May 30] .
• Centers for Disease Control and Prevention. Health Alert Network 00507: Adverse Effects Linked to Counterfeit or Mishandled Botulinum Toxin Injections . CDC; 2024 Apr 23 [cited 2026 May 30] .
• British Association of Aesthetic Plastic Surgeons. Botulinum toxin injections . BAAPS; [cited 2026 May 30] .
• Cleveland Clinic. Botox: What it is, results and side effects . Cleveland Clinic; 2022 Apr 6 [cited 2026 May 30] .