What Happens After Years of Treatment?

Botulinum toxin injections are widely used in aesthetic medicine to soften facial wrinkles and dynamic expression lines. While most patients are familiar with the short-term effects of treatment, many wonder about the long-term impact of repeated injections over several years.

Can regular treatment slow the formation of wrinkles? Does the effect weaken over time? Are there long-term safety concerns?

Clinical observations and long-term studies provide valuable insight into how repeated treatments influence facial aging.

This article explains the science, mechanisms, and long-term outcomes of botulinum toxin treatment, based on published medical research and clinical evidence.

How Facial Wrinkles Form

Many visible facial lines develop from repeated contraction of specific facial muscles.

Over time, dynamic lines that appear only during facial movement can become static wrinkles, meaning they remain visible even when the face is at rest.

The most commonly affected areas include:

Forehead Lines

Caused by contraction of the frontalis muscle, responsible for raising the eyebrows.

Glabellar Lines (Frown Lines)

Formed by repeated contraction of the corrugator supercilii and procerus muscles, which pull the eyebrows downward and inward.

Crow’s Feet

Created by contraction of the orbicularis oculi muscle during smiling or squinting.

Repeated muscle contraction gradually causes:

• Collagen breakdown

• Skin folding

• Dermal thinning

• Permanent wrinkle formation

These long-term lines are sometimes called “imprinted wrinkles.”

How Botulinum Toxin Works

Botulinum toxin works by temporarily blocking acetylcholine release at the neuromuscular junction, preventing the targeted muscle from contracting fully.

This leads to:

• Reduced muscle movement

• Smoother skin surface

• Softening of dynamic wrinkles

The effects usually begin within several days and last approximately 3 to 6 months in most patients.

Once the nerve signal gradually returns, muscle movement resumes and wrinkles may slowly reappear.

What Happens With Long-Term Treatment?

While short-term effects are well understood, researchers have also investigated what happens when patients receive treatments regularly for many years.

One particularly interesting clinical observation compared identical twin sisters, where one twin received regular treatment for over a decade and the other did not.

Evidence From a Long-Term Identical Twin Study

A published medical report compared 38-year-old identical twins, where:

• One twin received injections 2–3 times per year for 13 years

• The other twin received only two treatments over the same period 

This unique comparison allowed researchers to evaluate the long-term effects of repeated treatment while controlling for genetics and lifestyle.

Key Findings From the Study

Forehead and Frown Lines

The twin who received regular treatment did not develop visible forehead or glabellar wrinkles at rest.

In contrast, the minimally treated twin showed clear static wrinkles in these areas. 

This suggests that long-term treatment may prevent the formation of permanent expression lines.

Crow’s Feet

Crow’s feet were also reduced in the regularly treated twin when smiling, even though treatment in that area had only been started in recent years.

Untreated Areas Aged Normally

Interestingly, areas that were not treated — such as the nasolabial folds — appeared similar in both twins.

This indicates that the differences in wrinkle formation were specifically related to the treated muscles, rather than differences in general aging.

Why Long-Term Treatment May Slow Wrinkle Formation

Repeated treatment appears to affect facial aging through several mechanisms.

1. Reduction of Repetitive Skin Folding

Constant muscle contraction folds the skin thousands of times per day.

Over years, this mechanical stress leads to:

• dermal collagen breakdown

• permanent skin creasing

• deep wrinkle formation

Reducing muscle activity limits this repetitive folding process.

2. Prevention of “Imprinted Lines”

When expression lines are repeatedly formed, the skin eventually retains the crease even when the face is relaxed.

These are known as imprinted wrinkles.

Long-term treatment appears to delay or prevent the development of these permanent lines. 

3. Behavioural Muscle Retraining

Another proposed mechanism is neuromuscular habit change.

Patients who receive regular treatment often develop the habit of not over-contracting certain facial muscles, even when the toxin effect wears off.

This behavioural change may further reduce wrinkle formation over time.

4. Reduced Mechanical Stress on Skin

By reducing repetitive contraction, there may be less mechanical pressure on the dermis.

Some researchers suggest this may support dermal remodeling and skin recovery over time.

Does Botulinum Toxin Stop Working After Many Years?

One common concern is whether the treatment becomes less effective with repeated use.

Clinical studies suggest this is generally not the case.

In long-term treatment observations:

• Duration of effect remained stable

• Dose requirements did not significantly increase

• Clinical results remained consistent over many years

Some reports even suggest that repeated treatments may enhance treatment response and prolong duration.

Long-Term Safety Profile

Botulinum toxin has been extensively studied for both medical and aesthetic use.

Long-term clinical observations have shown:

• High patient satisfaction

• Good tolerability

• Low incidence of serious adverse effects

In the identical twin study described above, no adverse effects were reported during 13 years of regular treatment. 

When administered appropriately by trained medical practitioners, the treatment is considered to have an acceptable safety profile.

What Happens If You Stop Treatment?

If treatment is discontinued:

• Muscle activity gradually returns

• Dynamic wrinkles may reappear

• Skin aging continues naturally

However, patients do not typically appear worse than if they had never received treatment.

In many cases, patients simply return to the natural aging process.

How Often Is Treatment Usually Done?

Most patients receive treatment approximately every:

3 – 6 months

The exact interval depends on:

• muscle strength

• dose used

• treatment area

• individual metabolism

Long-term treatment plans are usually individualised by the treating doctor.

Common Treatment Areas

Botulinum toxin is commonly used to treat:

Upper Face

• Forehead lines

• Frown lines (glabellar lines)

• Crow’s feet

Lower Face

• Downturned mouth corners

• Chin dimpling

• Neck bands

Each area requires specific anatomical knowledge and precise dosing.

Who May Benefit From Early Preventative Treatment?

Some patients choose to begin treatment before deep wrinkles form.

Preventative treatment may be considered in patients who:

• develop strong expression lines early• have visible wrinkles during facial movement• want to delay permanent wrinkle formation

Early treatment may help reduce the progression of dynamic lines into static wrinkles.

Frequently Asked Questions

Does Long-Term Treatment Make the Face Look Unnatural?

When administered appropriately, the goal of treatment is to soften excessive muscle activity while preserving natural expression.

Modern aesthetic practice typically uses lower, customised doses to maintain a natural appearance.

Can Wrinkles Become Permanently Prevented?

Treatment does not stop aging entirely.

However, evidence suggests it may slow the formation of certain expression-related wrinkles.

Can the Body Become Resistant?

Resistance to botulinum toxin is rare in aesthetic use, particularly when treatments are spaced appropriately.

Key Clinical Takeaways

• Facial wrinkles are often caused by repeated muscle contraction

• Botulinum toxin reduces muscle activity and softens expression lines

• Long-term treatment may prevent the formation of permanent wrinkles

• Repeated treatments appear to maintain effectiveness over time

• Clinical observations show good long-term safety when administered appropriately

Disclaimer:The information provided in this article is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. The content is not intended to be a comprehensive source of information and should not be relied upon as such. Reliance on any information provided in this article is solely at your own risk. The authors and the publisher do not endorse or recommend any specific tests, physicians, products, procedures, opinions, or other information that may be mentioned in the article. Any reliance on the information in this article is solely at the reader's own risk.