This question comes back again and again — and that’s a good thing.
The answer is not black and white, and scientific literature reveals far more than what we usually hear during a cosmetic appointment.

What studies have actually shown:

✅ Botulinum toxin type A causes chemical denervation of the muscle.
This means the nerve signal is blocked — and by definition, this leads to muscle atrophy.

✅ Atrophy has been observed after a single injection.
Documented in both animal and human studies through ultrasound, MRI, and histological analysis.

✅ A reduction in muscle volume and fiber cross-section has been consistently reported.
The muscle is not simply “resting.” It loses mass, and its strength can remain decreased even after the wrinkle-smoothing effect fades.

✅ These changes do not always fully reverse.
Some studies show only partial recovery.
When Botox is used repeatedly over years, the structural changes may accumulate.

✅ Molecular and gene-expression changes have also been documented.
This suggests the muscle may be reprogrammed, not just temporarily switched off.

❌ Conclusion from scientific reviews:
Muscle atrophy after Botox can be long-lasting, and full reversibility is not guaranteed, especially with repeated injections.