There's honestly no 'too young' rule set in stone — it really comes down to your individual skin and what's bothering you. Some people start in their late 20s as a preventative measure, others wait until lines become more prominent. The key is having a realistic conversation with a licensed injector who can assess your face and explain what results are achievable. Botox works really well for dynamic lines — the ones that form when you move your face, like squinting or raising your eyebrows. A good practitioner will tell you honestly whether it makes sense for you or not.