Long-term effects of botulinum toxin type A (Botox) on facial lines: a comparison in identical twins.
Level 4 - case-series / case-control
Single-pair identical twin case comparison
PubMed 17116793 · doi:10.1001/archfaci.8.6.426
What was done
Identical twin sisters were evaluated for facial line development after divergent long-term exposure to botulinum toxin type A (Botox). One twin received Botox injections in the forehead and glabellar region 2 to 3 times per year for 13 years, plus crow's feet treatment twice in the preceding 2 years. The control twin received Botox only twice (3 and 7 years prior in the forehead and glabella). Imprinted lines at rest, dynamic crow's feet upon smiling, and untreated areas (nasolabial folds) were compared.
What was found
No quantitative measurements or statistical tests were reported in the abstract. Imprinted forehead and glabellar lines were not evident in the regularly treated twin but were evident in the minimally treated twin. Crow's feet were less noticeable when smiling in the regularly treated twin (noted at 7 months after treatment). Untreated facial areas such as nasolabial folds showed comparable aging in both twins. Neither twin experienced adverse effects.
Why it matters
This longitudinal co-twin comparison provides proof-of-concept evidence that sustained neuromodulator treatment over more than a decade can prevent the development of permanent resting facial lines.
Limits
The study examines only one pair of twins (n = 2), precluding statistical analysis or broad generalization. Outcomes are reported purely qualitatively without blinded assessment or objective skin imaging, and potential lifestyle confounders over the 13-year period are not accounted for in the abstract.
Cited by
- supports Repeated dynamic facial expressions cause inset facial wrinkles, which is why paralyzing movement with Botox prevents wrinkle formation.